Kojima, Japan — selvedge denim since 1992

Japan Blue Jeans

Japan Blue Jeans is a Kojima brand. That matters because Kojima is not simply a place where denim is made — it is the town that spent four decades building the infrastructure, the expertise, and the culture that defines Japanese selvedge denim. Japan Blue grew from that environment, developing original fabrics, refining a small family of cuts, and building a range that extends from classic indigo denim into workwear-derived jackets, pants, and outerwear.

The brand is now at a turning point. Japan Blue has already relaunched in Japan, with new flagship stores open in Osaka and Fukuoka and a new direction underway. The range available at URAHARA is the final production run of the current era — the denim, the Sashiko line, and the full pants program as Japan Blue built them before the pivot. This page covers what the range is, how it works, and what makes it worth understanding before it is replaced.

+ Kojima and the making of Japanese denim

Kojima is a small coastal city in Okayama Prefecture, and it is the closest thing the denim world has to a single origin point for Japanese selvedge production. The town developed its textile industry through the twentieth century — starting with school uniforms, building toward workwear, and eventually becoming the base for a generation of denim brands that chose craft over volume when the rest of the industry moved toward mass production.

Japan Blue Co., Ltd. was founded in Kojima in 1992. The company operates both Japan Blue Jeans and Momotaro Jeans, each with a distinct positioning. Momotaro carries the premium heritage line — heavier fabrics, more elaborate construction details, higher price points. Japan Blue sits alongside it as an independent brand in its own right: original fabrics developed specifically for the label, a focused range of cuts, and pricing that makes Kojima-made selvedge denim genuinely accessible without compromising on manufacturing.

The shared infrastructure matters. Japan Blue draws on the same Kojima supply chain — the same mills, the same shuttle looms, the same finishing expertise — but uses fabrics and constructions developed independently for the label. The two brands are related by ownership and geography, not by product. Buying Japan Blue is not buying a budget version of Momotaro. It is buying a different thing made in the same place by the same people.

Shuttle looms, Kojima — Japan Blue fabric in production

Two cotton origins. Two fabric characters. One numbering system.

+ The fabric system: US cotton and African cotton

14.8oz US Cotton — the J3xx and J4xx series
Japan Blue's US cotton fabric is woven from American short-staple cotton rope-dyed in indigo, then woven at slightly higher tension on vintage shuttle looms for a tight, dense weave. At 14.8oz it sits in mid-weight territory — substantial enough to develop strong fades, light enough for year-round wear in most climates. The fabric is sanforized, meaning it will not shrink significantly after washing. Expect a structured hand that softens considerably with wear, and fades that develop along high-stress lines — thighs, seat, knees — with good contrast.

12.5oz African Cotton — the J3xx and J4xx Africa series
The African cotton fabric uses longer-staple cotton from the African continent, known for producing a softer, more supple hand from the start. At 12.5oz it is noticeably lighter than the US cotton — more comfortable in warmer weather, and easier to break in for wearers who find raw denim's initial stiffness a barrier. The fabric still rope-dyes well and fades cleanly, but the character is less rugged and more refined. Both raw and mid-wash versions are available in the current range.

14oz Black Selvedge — the J414
The J414 uses a 14oz sulfur-dyed black selvedge. Black selvedge denim fades differently from indigo — the black breaks down toward grey and brown tones rather than the classic blue-white contrast of indigo fades. It is a less common fabric in the selvedge world and gives a cleaner, more contemporary look than the standard indigo range.

17oz US Cotton — the J427
The J427 is the heavyweight outlier in the Japan Blue denim range. At 17oz it uses the same American cotton base as the 14.8oz fabric but woven heavier for a stiffer hand, more pronounced texture, and slower, deeper fades. This weight takes longer to break in and rewards patient wear — the kind of jeans built to look better after two years than they do on day one. The J427 uses the Classic Straight (J4xx) silhouette.

How the numbering system works
Japan Blue's model codes are logical once you know the key. The first digit after J indicates the silhouette: 3 = Slim Straight, 4 = Classic Straight, 5 = Loose Fit. The second digit indicates the fabric generation or variant. So J301 and J304 share the same Slim Straight cut — one in US cotton, one in African cotton. J401, J404, and J427 are all Classic Straight, in different fabrics. J501 and J504 are both Loose Fit. Once you know the silhouette you want, the fabric choice is a separate decision.

J401 Classic Straight — 14.8oz US cotton, raw

+ Three cuts, one logic

Japan Blue builds its denim range around three silhouettes, each available across multiple fabrics. The cuts are not trend-driven — they are a stable set of shapes covering the main territory of how people actually wear jeans.

The Slim Straight (J3xx series) is the most contemporary of the three. It sits closer to the body through the thigh and tapers to a slim but not skinny leg opening. It reads cleanly, works across a wide range of body types, and suits wearers who want Japanese selvedge denim without a conspicuously vintage silhouette. The J301 in 14.8oz US cotton and the J304 in 12.5oz African cotton are both slim straight cuts.

The Classic Straight (J4xx series) is the reference point of the range. More room through the seat and thigh than the slim straight, with a leg that runs parallel from knee to hem. This is the cut closest to the American workwear jeans that Kojima manufacturers have always used as their touchstone — a shape that has been worn by people doing actual work since the 1940s and has not dated because it was never fashionable to begin with. Available in 14.8oz US cotton (J401), 12.5oz African cotton (J404), 14oz black (J414), and 17oz US cotton (J427).

The Loose Fit (J5xx series) is the widest cut — more room everywhere, a higher rise, and a straighter, more generous leg. It reads closer to vintage workwear or military surplus than contemporary denim, and suits wearers who prioritise comfort or prefer a more relaxed silhouette. Available in 14.8oz US cotton (J501) and 12.5oz African cotton (J504), in both raw and mid-wash versions.

Japan Blue Sashiko Chore Coat — 11oz indigo dobby

+ Beyond denim: Sashiko and the workwear range

Japan Blue's range extends well beyond jeans. The Sashiko line is the most distinctive part of it — a series of garments built from an original 11oz indigo dobby fabric that references the traditional Japanese reinforcement-stitching textile known as sashiko. The fabric has a visible woven texture created by its dobby construction, and it is dyed in indigo to give it the same tonal character as the denim range. It is lighter and more drapey than denim, suited to layering, and it ages differently — the texture gradually softens and the indigo fades in a more even, diffuse way than the high-contrast fading you get from rope-dyed selvedge.

The Sashiko Chore Coat is the standout piece — a single-breasted work jacket with a clean, boxy cut and functional chest pockets. The chore coat form comes from French bleu de travail workwear, and Japan Blue's version sits between a traditional coverall jacket and a contemporary overshirt. It works as outerwear in mild weather and as a mid-layer in the cold. The Sashiko Type 2 Jacket in black uses the same fabric in a cropped, fitted cut that reads more as a denim jacket replacement than a workwear piece. The Sashiko Wide Tapered Pants complete the set — cut wide through the thigh and tapered to the ankle, they sit comfortably alongside both the denim range and the chore coat.

The non-Sashiko pants program rounds out the workwear side of the brand. The Modern Military Baker Pants and M-65 Cargo Pants use military-derived patterns in cotton fabrics — the Baker in a standard cotton twill, the M-65 in a 9.5oz ripstop. The French Work Serge Baker Pants use a navy twill that references European workwear rather than American military surplus. The Wide Carpenter Pants are cut in a lightweight 10oz denim with a wide, straight leg and the carpenter-style patch pockets that come from American workwear tradition. Together these give Japan Blue one of the broader non-denim pants offerings of any brand in its category.

Japan Blue Jeans

27 items

Japanese Selvedge Denim

49 items

MOMOTARO JEANS

11 items

+ The final run — what this delivery represents

Japan Blue has already rebranded in its home market. New flagship stores have opened in Osaka and Fukuoka with a repositioned identity and a new product direction. The range as it has existed — the US and African cotton denim cuts, the Sashiko line, the military-inspired pants — is the era that is ending.

The delivery currently at URAHARA is the final production run of this range. When it is gone, it will not be restocked in its current form. The new direction from Japan Blue will arrive in August and September, and it will be a different product at a different price point aimed at a different customer.

That is not a reason to rush a purchase, but it is context worth having. If you have been considering a pair of J401s or a Sashiko Chore Coat, this is the last time the current versions will be available. What replaces them will be its own thing — we will carry it, and we will write about it when it arrives. But it will not be this.

+ Frequently Asked Questions

Both brands are made by Japan Blue Co., Ltd. in Kojima, Okayama, and both use Japanese selvedge denim. However, they are independently developed ranges — different fabrics, different cuts, different price points, and different positioning. Momotaro is the premium heritage line, with heavier fabrics, more elaborate construction details, and higher prices. Japan Blue uses fabrics developed specifically for the label and sits at a lower price point without compromising on manufacturing location or method. Buying Japan Blue is not buying a budget version of Momotaro — it is a different product from the same factory town.

It depends on what you want from the fabric. The 14.8oz US cotton is denser and more structured — it takes longer to break in but develops stronger, more contrasted fades over time. The 12.5oz African cotton uses longer-staple fibres that produce a softer, more supple hand from the start. It is more comfortable in warmer weather and easier to wear immediately. Both are selvedge denim woven on shuttle looms in Kojima. If you want the classic raw denim experience and patience to break them in, the US cotton. If you want something that feels refined from day one and suits a wider range of conditions, the African cotton.

The Slim Straight (J3xx) sits closer to the body through the thigh and tapers to a slim leg opening. It is the most contemporary-looking of the three and works across a wide range of body types. The Classic Straight (J4xx) has more room through the seat and thigh with a parallel leg from knee to hem — it is the reference-point cut, closest to the American workwear jeans that Japanese denim has always referenced. The Loose Fit (J5xx) is the widest, with a higher rise and a generous straight leg — best for wearers who prioritise comfort or prefer a vintage workwear silhouette. If unsure, start with the Classic Straight. It is the most versatile of the three.

The current Japan Blue range uses sanforized denim, which means the fabric has been pre-shrunk during finishing. You should not experience significant shrinkage after washing — sizing to your normal waist measurement is appropriate. This is different from unsanforized (also called 'loomstate' or 'shrink-to-fit') denim, which requires sizing up to account for post-wash shrinkage. If in doubt about a specific model, get in touch and we can advise on fit based on the measurements you have.

Sashiko is a traditional Japanese textile technique involving dense, repetitive stitching patterns used originally to reinforce and insulate work garments. Japan Blue's Sashiko fabric references this tradition through its weave structure — it is an 11oz indigo-dyed dobby cotton with a visible textured pattern woven into the cloth. It is not stitched in the traditional sashiko method, but the fabric character and indigo dyeing give it a similar visual quality. It is lighter and more drapey than denim, ages with a softer, more even fade, and works well as a layering piece or standalone jacket fabric.

For raw denim, the standard advice is to wear as long as possible before the first wash — the longer you go, the more defined the fades will be when they appear. When you do wash, turn inside out, use cold water, a gentle detergent, and hang to dry away from direct sunlight. Do not tumble dry. For the washed versions (mid-wash) there is less ceremony required — treat them as you would any quality cotton garment. Avoid hot washing and tumble drying regardless of the fabric version, as heat will break down the cotton fibres faster than wear will.

Yes. Japan Blue jeans are made in Kojima, Okayama Prefecture, Japan. Kojima is the primary centre of Japanese selvedge denim manufacturing and has been since the 1960s. The fabrics are woven on vintage shuttle looms in the region, and the garments are constructed in Japanese factories. Japan Blue Co., Ltd. has been based in Kojima since its founding in 1992.

Japan Blue has repositioned as a brand in its home market, with new flagship stores opened in Osaka and Fukuoka and a new product direction underway. The range currently available at URAHARA — including the US and African cotton denim cuts, the Sashiko outerwear line, and the full pants program — is the final production run of the pre-rebrand era. The new direction will begin arriving at URAHARA in August and September 2026. We will carry both eras as they transition. The current range will not be restocked once it sells through.

Yes. We offer chain-stitch hemming and alteration services for all denim purchased from URAHARA, including Japan Blue. Chain-stitch hemming preserves the original hem character of the jeans and is the correct finish for Japanese selvedge denim. If you are unsure of your inseam length, we can advise — it is always better to hem after washing if you are buying raw denim, as the leg length will be stable by that point.