mohy reblogged

Yoruichi Combat Uniform Recognition Guide

It’s possible to describe the nature of Yoruichi’s outfits over time purely through text, but visual examples are useful for understanding the differences between them. Beyond that, several things can be learned about her and the types of resources available to her from studying them.

Although there are no official designations for her outfits, for the purposes of this post, major divergences and their modifications will be labeled with a fairly simple designation scheme.

Mk. 1 Mod. 0 (chapter 130, page 10)

Yoruichi’s first chronological appearance also gives us her first combat uniform. This is an Onmitsukidō design. The upper half of this outfit is substantially similar to other stereotypical “shinobi” outfits, such as the original outfits for Kasumi from Dead or Alive. (Vaguely NSFW reference on how that outfit would be put on can be found here, with Yoruichi’s likely similar). It appears to be quite similar in design to the tops used by the Inner Court Force. This uniform consists of:

Uwagi: white, tight and shortened sleeves (note the lack of excess material at the elbows), flap extensions at the front and back to cover the groin and rear
Unknown-style Top: black, thin material, mock neck, short sleeves or sleeveless (note the bare forearms), possibly a crop-top (note the high waist); likely comparable to a mock neck dance crop top (like this)
Obi: white, standard size; typical Japanese sash
Fundoshi: white, modified for women’s use; the uniform side-width and cultural context suggest this style of underwear (see also: Kūkaku, chapter 177, page 12), as panties didn’t exist in the West in their modern form until the 1930s; these may simply be side-ties for the kosode, as with Kasumi’s outfit, but seem more likely to directly be her underwear given their broad similarity to what’s seen with Mk. 2 Mod. 0
Boots: black, thigh high, short-heeled; seemingly of single-body construction, these might at first seem to be stockings, but there’s no obvious break where footwear would end and the legging would begin, and this style will return later

Mk. 1 Mod. 1 (chapter 159, page 16)

Substantially similar to Mk. 1 Mod. 0, there are nonetheless a few changes by this time. It’s notable that Yoruichi is continuing to use this overall uniform pattern given she’s both the Sōshireikan of the Onmitsukidō and 2nd Division Taichō by this time; it’s also interesting that she’s using a uniform of the former organization after having also joined the Gotei 13. Some additional analysis of this uniform and the previous one, especially vis-à-vis the uwagi, may be read here.

Uwagi: orange, mid-length sleeves, silver/white constructions on the shoulders (pteruges); this is the first chronological appearance of Yoruichi’s signature jacket style, which hasn’t visibly changed much since its introduction other than the deletion of the front and rear flaps and the occasional lengthening of the sleeves (note that they are still shortened here); this almost certainly serves as an indication of her rank and unit (see the link above); the flaps are notably missing in the rest of Soifon’s memories of Yoruichi, suggesting “fully modern” variants were soon available to be paired with Mk. 2 Mod. 0
Unknown-style Top: this top is likely the keisen shōzoku top seen with Mk. 2 Mod. 0, paired with similar gloves, and Soifon’s other flashbacks in chapter 159 would suggest this as well; however, there is a distinct possibility that it’s a long-sleeve top like that seen with Mk. 4 Mod. 0, like a modification of that seen with Mk. 1 Mod. 0
Boots: The white hem at the top of the boots visible in Mk. 1 Mod. 0 has been deleted

Mk. 2 Mod. 0 (chapter -105, page 11)

Yoruichi’s official shihakushō during her time with the Gotei 13. It’s unknown if she wore other variations before this. While she wears the haori for official occasions (as is typical for that garment), she seemingly eschews it while at the 2nd Division, preferring her uwagi (as can be seen in Soifon’s flashbacks in chapter 159). Other than having an orange lining (as is typical for 2nd Division since it’s their unit color), nothing distinguishes the haori as unique. Other elements include:

Ribbon: black, front-tied, personal affectation (Yoruichi seems to like having fabric at her lower neck)
Keisen Shōzoku Top: black; a customized top designed to reveal the back and shoulders for Shunkō, it seems to be a modified kosode and shitagi from a shihakushō; as a backless, sideless, halter design, in order to mechanically tension it properly across her bust it needs a very wide obi; the shitagi might be a real separate liner as in a standard shihakushō, it may be attached to but removable from the keisen shōzoku, or it may be a permanently attached affectation to mimic Shinigami styling; the second seems most likely in terms of both practicality and the fact there’s no evidence for a shitagi visible in the side slits of the hakama
Gloves: black, mid-bicep length, with integrated coverage for the wrist and sides of the hand; these gloves appear to be an Onmitsukidō specialty design, and are notable both for how they partially cover the hand, and their triangular cutouts there (presumably to improve side-to-side hand motion at the wrist)
Obi: white, notably wider than usual (on the order of 3–4x that normally seen in women’s shihakushō), but otherwise a typical Japanese sash; in addition to holding up the hakama, this appears to have been made much larger than typical to properly tension the keisen shōzoku
Fundoshi: white, modified for women’s use; these appear identical to what’s seen in the Mk. 1 series, and to the ones seen in Soifon’s uniform; their appearance through the slits of the hakama and visual similarity to those on the Mk. 1 series suggests these are indeed fundoshi rather than a tensioning element, as the hakama are instead held up by the obi
Hakama: black, modified from typical shihakushō design; standard hakama have widely flared bottom hems, whereas those of the Onmitsukidō abruptly cinch in at the ankles and then seem to loop about the arch of the foot or the heel in order to provide superior mechanical tensioning for combat. Yoruichi’s end in stirrups around the arch of the foot (like this); she doesn’t wear tabi socks with them (whereas Soifon does)
Kung Fu Shoes (not visible): black, traditional design (see here); presumably selected for superior striking power versus typical waraji sandals, and superior stealth versus geta shoes

Mk. 3 Mod. 0 (chapter -97, page 15)

The first (and only) dedicated sneaking suit of Yoruichi’s which we see, this design is only seen during the Central 46 trial breakout. (See CAT-2 here for an analysis of that event). It appears to have been made for some other, more standardized and official use, given its retention of standard shihakushō elements such as the collar and obi.

Head Wrap and Cloak: white, stealth element; likely the same material as Yoruichi’s hair wrap, later wraps on the Mk. 4 Mod. 1, Mk. 4 Mod. 2, Mk. 5 Mod. 0, and Kūkaku’s wraps (with this material being discussed more later)
Ribbon (not visible): identical to that seen on the Mk. 2 Mod. 0
Long-sleeve Top: black; this seems similar to both the top used with Mk. 1 Mod. 1, and with Mk. 4 Mod. 0 and Mk. 4 Mod. 2; it’s unclear if the gloved ends, which are similar to the gloves of Mk. 2 Mod. 0, are a new addition or a carryover from Mk. 1 Mod. 1; it has a standard shihakushō collar, complete with shitagi, similar to the standard rank-and-file Onmitsukidō uniform, although it appears to be cut tighter and more fitted
Obi: white, wider than usual but not as wide as that worn with Mk. 2 Mod. 0, likely due to a diminished need for mechanical tensioning with friction and the sleeves keeping the top largely secure by themselves
Shinobi Shōzoku Bottoms: black, elastic, likely stirruped; as can be visibly seen in both this appearance and with Mk. 4 Mod. 0, this material conforms tightly to Yoruichi (such that she seems not to wear underwear with it) and stretches, yet is highly durable; although tights existed at this time, knit-weave technology was not common in Japan (being used mostly for socks and some underwear), stretch fabrics wouldn’t exist for more another 50 years on Earth, these do not seem to require much if any tensioning, and this material is combat-rated against strikes and other forms of damage which would destroy many conventional fabrics
Unknown-style Shoes: it is unknown what sort of footwear accompanied this uniform

Mk. 4 Mod. 0 (chapter 126, page 18)

The most iconic look of Yoruichi’s, this uniform is donned after her rescue of Ichigo and sported during the confrontation with Byakuya, during her training of Ichigo, and during her confrontation with Yammy. It incorporates and refines several elements from earlier uniforms.

Long-sleeve Top: black, elastic, mock-neck; this broadly resembles a turtleneck and appears to be made out of a stretchy fabric; it seems to be an even tighter-fitting “civilian” variant of the top used with the Mk. 3 Mod. 0, with Onmitsukidō and shihakushō elements removed
Uwagi: orange, long-sleeved; largely identical to the one seen with Mk. 2 Mod. 0, and broadly similar to the one seen with Mk. 1 Mod. 1 other than the flaps
Obi: orange, standard size; a typical design, the shift from white to orange is likely intended to further distinguish Yoruichi’s uniform from those of Shinigami (although this coloration is persistent for this variant across both the official colorization and the anime, I’ll always recolor it for more visual continuity)
Shinobi Shōzoku Bottoms: black, elastic, stirruped; identical to the ones seen with Mk. 3 Mod. 0; we can observe that Yoruichi doesn’t wear underwear with these due to how tightly they fit, and their removal seems to indicate they’re made of a four-way stretch fabric
Greaved Shoes: white, flats, armored; the armored plates on these are clearly intended to enhance the striking power of kicks

Mk. 4 Mod. 1 (chapter 154, page 13)

The second most iconic of Yoruichi’s outfits, this variant is used exclusively for her fight with Soifon and has been customized with that confrontation in mind. (See CAT-4 here for an analysis of that fight.) It represents the first modern example of a more serious combat outfit, although it is evidently a hasty modification using supplies on hand. (Also note the hakama of the Onmitsukidō member at right, verifying the notes with the Mk. 2 Mod. 0 regarding this sort of hakama being standard for them.)

Neck Gaiter: tan, likely for neck protection; this material is visually consistent with other elements of this uniform, and with Yoruichi’s hair wrap, implying they are all made of the same material; it seems evident this kind of cloth has notable protective capabilities against blunt force impacts, Kidō (to include Shunkō, which it survives largely unscathed), and possibly also piercing and slashing attacks
Keisen Shōzoku-style Bodysuit: black, elastic; a “civilian” variant on the keisen shōzoku, this nonetheless likely includes several additional features beyond deleting the shihakushō elements; as a mock neck design which is a backless, sideless halter design, it’s implausible that it’s held in place and tensioned by such a slim obi, and in order for it to fit properly across her bust it would likely need to be a bodysuit (like this) which presages later outfits like the Mk. 5 Mod. 0 and Mk. 6 Mod. 0; it likely has snaps at the crotch for practicality’s sake
Uwagi: orange; this uwagi is almost identical to that seen with the Mk. 4 Mod. 0, except it seems to have shorter sleeves
Obi: tan; this obi is almost identical to that seen with the Mk. 4 Mod. 0, except its tan coloration suggests it’s made of a different, reinforced material, like for similar reasons as the other pieces
Gloves: black, full finger coverage; the first instance of Yoruichi wearing full gloves, this design will later be carried over into the Mk. 5 Mod. 0
Arm Wraps: tan, bound with pastel purple; these are almost certainly designed to protect her arms during strikes
Shinobi Shōzoku Bottoms: black, elastic, likely stirruped; seemingly identical to those on the Mk. 4 Mod. 0
Gaiters: tan; like with all the other elements, these seem to be there for protective purposes; their selection over the greaved shoes of Mk. 4 Mod. 0 suggests that this fabric is both actually stronger than those rigid plates, and more protective against a combatant like Soifon
Boots: brown; likely selected for superior protection and integrated weaponry (i.e., the anken)

Mk. 4 Mod. 2 (Chapter 226, Page 04)

A minor variant seen after Yoruichi’s recovery from fighting Yammy, this design mixes elements of Mk. 4 Mod. 0 (such as the long-sleeved top) with elements from Mk. 4 Mod. 1 (such as the scarf and gaiters). Novel elements seem to be variants on the shoes from the former, and variants on the gaiters from the latter (note that the fabric is white rather than tan). This design exists for more comfort while maintaining some degree of martial readiness, and tells us quite a lot about Yoruichi’s preferences when it comes to “casual” wear.

Mk. 5 Mod. 0 (chapter 403, page 16)

The first truly dedicated battle suit of Yoruichi’s which we see, this design was used against Aizen, although it seems intended to have been employed against the Espada. Many features from prior uniforms return in this design.

Neck Gaiter: tan; seemingly a carryover from the Mk. 4 Mod. 1 and Mk. 4 Mod. 2, it seems to be somewhat worse for wear on arrival, suggesting it’s seen some more use
Bodysuit: black; this is likely a more combat-oriented derivative of the keisen shōzoku-style bodysuit from the Mk. 4 Mod. 1, reengineered strictly for fighting; it is visibly more substantially built, with two pteruges-like structures at the hips and some layering to it
Gloves: black; these appear to be derived from those of the Mk. 2 Mod. 0, with the hand and finger elements of the Mk. 4 Mod. 1; they notably take comparatively little damage from Aizen’s attacks despite not being protected by the armor, and Yoruichi is unscathed where they break
Leggings: black; these appear very similar to those of the Mk. 1 Mod. 1, although they don’t seem to have soles, being more like leggings; like the gloves, these take comparatively little damage from Aizen’s attacks, with Yoruichi unscathed where they break
Anti-Hierro Armor: gray, “iron”; clearly designed for bludgeoning attacks, this was evidently made in response to Yoruichi’s experiences with Yammy and seems to have been made explicitly for beating Espada into submission (as killing them presents a problem to the balance of souls); it was pressed into service against Aizen as a stopgap measure

Mk. 6 Mod. 0 (chapter 657, page 01)

The second dedicated battle suit, this design represents an iteration of and improvement upon the Mk. 5 Mod. 0, with numerous differences separating the two, and with several callbacks to earlier designs as well. It was initially paired with an orange, short-skirted, sleeveless dress and a beige cloak which resembled the kind used for Shinigami expeditions to Hueco Mundo (see here), although it was parted in the opposite direction.

Bodysuit: black; this design is different than that of the Mk. 5 Mod. 0, with different structure at the hips (there are now four pteruges), less segmentation across the torso, and circular elements of unknown purpose added to the base of the neck
Gloves: black, forearm length, with integrated coverage for the wrist and sides of the hand; these gloves resemble shorter versions of the Onmitsukidō design from the Mk. 2 Mod. 0, although they lack the triangular cutouts; Yoruichi is missing the left glove in the reference image above as it was lost after she tore off her own arm (and had it restored by Orihime) following an attack from Pernida; the left glove notably sustained no damage at all from that attack, and it’s possible the right survived the activation of Raiju Senkei as it would’ve been fully covered by it
Boots: black; substantially similar those of the Mk. 5 Mod. 0, these nonetheless hearken back even more to the Mk. 1 Mod. 0 and Mk. 1 Mod. 1 as they incorporate soles—they are proper boots; they notably survived the activation of Raiju Senkei completely unaltered and unaffected

Implications for Yoruichi

All of Yoruichi’s combat uniforms together allow us to begin to build up a fairly cohesive picture of her physical preferences when it comes to battlefield attire, and likely with clothes in general outside of truly mundane civilian scenarios.

It should first be noted that tight and revealing clothing actually makes quite a lot of sense for superpowered individuals (see here for arguments on why), which Yoruichi certainly qualifies as by human standards. Her reiatsu output in fighting condition (i.e., not during the Soul Society arc, see here and here for details), while not as high as Kenpachi’s, should produce similar effects and make her largely invulnerable to most strikes. (Yes, she was pierced by Soifon’s Shikai, but wasn’t even nearly in peak condition at that time.)

She’s already much more durable than most materials, and it’s clear that shihakushō offer no protection at all. The obvious solutions would thus be both, as the linked video points out, less clothing and more durable clothing when it is worn. These are exactly her solutions. Additional reasons for the former are covered below, and the nature of the latter and some other physical aspects of the material are covered in the next section.

It becomes fairly obvious that the first and foremost consideration for Yoruichi is flexibility: the ability to move freely. Whether it’s large sections missing around major joints (across the thighs and upper arms, near the hips and shoulders, across the rear and back), or the tendency toward tight-fitting but highly flexible clothing (as seen with her various gloves, pants, leggings, and boots), Yoruichi privileges the ability to move freely and accurately first and foremost, precisely because she is focused on unarmed martial arts on the battlefield.

The next thing that she obviously privileges is physical protection, both of vital areas and more especially of striking surfaces. The vital areas for a Shinigami are somewhat different than those of a human. For example, Yoruichi is stabbed in or near the heart by Soifon to no ill-effect; Yūshirō survives being shot three times in the heart by Askin; Rangiku and Izuru survive large sections of their torsos being destroyed; and so on and so forth. We’re told by Zommari that decapitation is the main way of ensuring that a Shinigami is dead, and unsurprisingly, Yoruichi seems to favor neck protection. Meanwhile, she very plainly likes to protect her arms and especially her legs.

An added and not immediately obvious benefit of extremely tight-fitting clothing is compression. Compression wear for humans prevents excess movement (limiting tissue damage and fatigue) and improves circulation. A conceivable benefit of it would also be reducing blood loss from injuries. (Note how quickly Yoruichi stops bleeding after being stabbed by Soifon, especially from deep punctures to her core.)

Finally, limited tight-fitting clothing exposing a lot of skin makes heat regulation easy, as it provides a lot of surface area with which to radiate heat through sweating, without having to worry about clothes becoming soaked with sweat (especially if the material is moisture-wicking). This combined with layering (another obvious reason for Yoruichi to wear her uwagi as a jacket and neck gaiter as a scarf) affords easy temperature regulation while maintaining good heat radiance during battle, reducing heat stress and preventing overheating.

Considering Yoruichi has no real problems with nudity, these additional reasons are likely why she fights wearing clothing at all rather than in the nude—her clothing is highly tuned and customized to provide additional benefits to her in combat scenarios.

Thoughts on Construction

Several things can be discerned about the Seireitei, the Shihōin, and possibly Yoruichi herself given the nature of her uniforms.

First and foremost, numerous elements of Yoruichi’s uniforms defy conventional explanations, and suggest that she has unique materials available to her that are not in common circulation within the Gotei 13, Onmitsukidō, Nobility, or the Seireitei at large. These include:

Unknown Tan Textile 1 (UTT-1): The tan material used for Yoruichi’s hair wrap and for various elements on the Mk. 4 Mod. 1, as well as the scarf from that outfit seen thereafter, seems to be extremely durable against shock and magic, and may also have utility against bladed weapons. Its sparing use suggests it’s difficult to fabricate, or otherwise has negative aspects that preclude truly comprehensive usage (such as being comparatively inflexible or retaining too much heat).
Unknown Black Textile 2 (UBT-2): The black, stretchy material used for various garments in the Mk. 3 Mod. 0 and Mk. 4 series has properties not found in materials of the time period in which it was first shown, superficially resembling materials such as nylon, knit silk, or lycra/spandex. Unlike those materials, it seems to be incredibly durable and able to resist stresses which would easily rip or tear those materials.
Unknown Black Textile 3 (UBT-3): The material used for the boots of the Mk. 1 series, and the whole outfit of the Mk. 5 Mod. 0 and Mk. 6 Mod. 0, seems to be even more substantial than UBT-2, resembling something more like neoprene than leather or vinyl. Its behavioral characteristics are advanced beyond even something like kevlar, however, as it very obviously is even more durable than UTT-1. Its real world equivalent is likely, at a minimum, something like spider silk.

Given that Yoruichi is known to have access to other unconventional materials and substances (such as what appears to be monomolecular filament during her her confrontation with Yhwach), her having access to materials which not only don’t seem to fit the setting and technology of the Gotei 13, but which are in advance of humanity not only at the time, but at present, is not unusual.

This becomes even less unusual when one accounts for exotic textiles like Byakuya’s scarf, made from ginpaku kazahana no uzuginu (銀白風花紗, “silvery-white windflower silk gauze”, henceforth GKU), which is evidently extremely expensive. It’s likely that that scarf isn’t only so expensive for its materials and labor, but likely has Kidō interwoven into it as well to protect it (and its wearer where it covers). Consider: how many Kidō masters are there, and how expensive would their time be to procure?

What is rather unusual, however, is that these materials are quite obviously not just uncommon in the Seireitei, but among those who could afford any expense like Byakuya. Byakuya himself is admittedly a traditionalist, and while Soul Society’s technology base seems to be at the level of feudal Japan, there are obviously exceptions (much more so recently), yet these materials involve even larger departures than is usual and their use is limited to only Yoruichi despite their obvious utility. This suggests likely only Yoruichi has access to them, through the Shihōin.

So, what is the point of divergence for these materials? Historically, the vast majority of clothes in Japan were made from hemp. A more detailed history from here follows:

From very ancient times until the 1600s, Japanese peasants wore clothing made from common hemp, a locally grown and processed bast fiber. Rural Japanese crafts women spun the hemp and hand loomed the fiber threads into usable fabric which was turned into everyday farm field clothing and household articles. The Japanese did not distinguish between linen and hemp, the two have similar fibers and appearance and are referred to by the same Japanese word, asa. Hemp fabric was the only material available for general use in Japan until the introduction of cotton. The Japanese imported raw cotton and finished cotton goods from China from the 15th century and also from India somewhat later. This situation lasted until 16th century when the Japanese adopted Chinese cotton cultivation methods and began to produce cotton domestically. Cotton farming quickly became established in the warmer western regions of the Japanese archipelago where the moderate climate and fertile land were well-suited for growing cotton plants.

[…]

By the 1870s, the Japanese had imported modern cotton milling equipment from Europe. This was done rather late when compared to the West where factory style milling was already well established. A few large commercial cotton spinning and weaving mills operated near Osaka. The initial production of milled cotton fabric was priced at a premium. This was due to the material’s excellent quality and high manufacturing expense. The price of cotton fabric was too costly for most ordinary Japanese who depended upon less costly homespun fabric. As a result, the large Japanese textile mills did not turn out the bulk of the cotton threads and fabric for the general marketplace of the period. That task remained firmly in the hands of the rural Japanese textile cottage industry, in the homes of the rural peasants.

A different source, here, tells us about the use of knit fabrics (meriyasu) in Japan:

Knitting was first introduced to Japan during the Nanban trade period (1543–1614 CE) when trade relations with Europe were established in earnest. The Japanese term for knitted fabric, meriyasu, is derived from the Portuguese word ‘meias’, meaning ‘socks’. Meriyasu specifically refers to fabric made using a plain stitch which can stretch in both horizontal and vertical directions. The first knitted items that entered Japan were primarily socks, gloves and undergarments; however, as the use and range of knitted fabric expanded to outerwear and non-clothing items, the term meriyasu became outdated and from mid-1950s the English word ‘knit’ came into the common vernacular.

Meriyasu production first began in Nagasaki, in the south of Japan, but soon spread to Edo, present-day Tokyo, where, due to the relative peace and stability of the Genroku era (1688–1704 CE), many samurai took up hand-knitting to supplement their income. The Meiji era (1868–1912 CE) brought in the abolition of the feudal clan system, leaving many low-ranking samurai out of work, and they turned to hand-knitting in even greater numbers. They worked with knitting needles and thin iron rods, using cotton and silk thread to make tabi, Japanese socks with a separate part for the big toe, undershirts, gloves for firearm handling, hilt and handguard covers for swords, and other items. Much of this production took place in the Honjo district, in eastern Tokyo, where many residences of feudal clan lords, daimyo, had been located and were now transformed into knitting factories.

The Meiji government recognized that the textiles industry was to play a big part in the industrialization of Japan, and actively encouraged mechanization and mass production of knitted fabric. State-run factories were established to lead and inspire private enterprise. In 1870 Japan’s first machine-made knitwear was produced by the entrepreneur Nishimura Katsuzō in Tokyo, after he purchased a new Komaru circular sock knitting machine from America; the following year, he purchased a new horizontal rubber knitting machine in order to improve the quality of his products. Following suit, many knitting factories equipped with similar machines were established in Honjo, which came to be regarded as the birthplace of Japan’s knitting industry. As the industry developed, different types of knitting machines came into use, such as double-sided and hanging knitting machines.

The existence of fundoshi in general, tabi socks for the Gotei 13, and stirrups for the Onmitsukidō’s hakama suggests that meriyasu-style knitwear is known and producible within the Seireitei. The fact that Shinigami seem to only come with one shihakushō (see the link provided with “Souls and Clothing” below) and likely need spares, the existence of Academy uniforms, and the need for clothes for the nobility, also suggests that demand exists. And the timeframe of Turn Back The Pendulum means it was occurring at a time when there should’ve been many Pluses who had formerly been samurai who were talented at knitting by hand. There was thus the possibility of, and supply and demand for, knit fabrics like those found in Japan.

However, machines for making knitwear were uncommon not just in Japan at this time, but globally. Machine production of meriyasu didn’t reach Wakayama, a key textile center in Japan, until 1909. So we can presume that a lot of such meriyasu fabric in Japan was done by hand, and this is likely even more true of Soul Society.

Given this, the existence of the Mk. 3 Mod. 0, which appears to be wholly knit, means it was likely either done entirely by hand, or the product of work on a machine (which would further suggest the Shihōin having a technological affinity and a drive to acquire specialist talent).

There is ample canonical suggestion that Yoruichi only occasionally went back to Soul Society from 1901 to 2001, and that many of the resources available to her while she was there during the Soul Society arc were prepositioned by her; this suggests she had access to resources, but probably limited access to R&D. In other words, it’s likely that the initial contemporary outfits we see her in (i.e., the entire Mk. 4 series) were made in Soul Society prior to the Hollowfication Incident. This means that all the shinobi shōzoku were likely made at the same time, of the same material (UBT-2) which has no equivalent among earthly textiles. If that’s the case, such a volume of clothing likely required machine production.

This also means that the keisen shōzoku-style bodysuit which is paired with the Mk. 4 Mod. 1 had also been developed even then, in the same way. Although a bodysuit made from UBT-2 would be much thinner than ones made from UBT-3, like the Mk. 5 Mod. 0 and Mk. 6 Mod. 0, it still would’ve presented an improvement over the tensioning system of the Mk. 2 Mod. 0, and permitted a return to a style clearly more to Yoruichi’s preference (i.e., that of the Mk. 1 Mod. 1). A UBT-2 bodysuit under UBT-2 shinobi shōzoku would likely not present a pantyline, and securing it is plausible as snaps (which would ideally be put at the crotch as in modern clothing like this) were first developed in 1885. The Mk. 5 Mod. 0 and Mk. 6 Mod. 0 were clearly made to carry this design forward and iterate upon it.

As for the materials, a plausible origin story is that UTT-1 was a low-cost alternative to GKU which was similar in protective power but inferior in other aspects, UBT-2 was a material superior in handling to GKU but inferior in protection to it or UTT-1 (notice that Soifon stabs through it with her Shikai), and that UBT-3 was nearly as good as UTT-1 and UBT-2 at their respective strengths but began to approach GKU in difficulty of manufacture, and thus had until recently only been used on boots (with kicks being Yoruichi’s main form of attack).

All of this makes good sense and is quite plausible if one assumes that the Shihōin are technically inclined and interested in innovating, which squares quite well with their position as Tenshiheisōban (天賜兵装番, Guard of Heavenly-granted War Machines), and as the caretakers of the Hōgu (宝具, treasured tools) and Bugu (武具, armaments). They clearly already have garments with interesting properties, and more than likely make them, “heavenly-granted” be damned.

Other Thoughts

Some other thoughts which don’t fit anywhere in particular:

Anime Versions: Many of the anime versions of Yoruichi’s outfits, like the Mk. 2 Mod. 0, Mk. 4 Mod. 1, and Mk. 5 Mod. 0, have a shitagi-style element to them for censorship purposes, giving the impression that the shitagi of the Mk. 2 Mod. 0 might be real (especially as it’s visible in the slits of the hakama, as on a normal shihakushō). I think the existence of this on other versions where there plainly is no shitagi is evidence that it isn’t, however, and that that is likely not a full garment.
Most Variations: Outside of Ichigo and perhaps Aizen (depending on how one counts), and disregarding changes to civilian clothing, Yoruichi probably has the most outfit variations of any character in Bleach.
Souls and Clothing: As noted in the post on Souls and Clothes, it’s curious that Yoruichi has no “set” outfit and seems to select hers manually.
Shutara: It’s plausible that, much as there is some connection between Kisuke—and likely, as in my headcanons, Yoruichi—and Kirinji, that there is a connection between the Shihōin and Shutara. This may all be technology adapted from hers, or she may have developed her own on the basis of precursors to their fabrics like GKU, in which case they’re more like parallel developments; more cannot be said other than that there is a link in the form of protective clothing.)