After Japan’s Defeat: The Beginning of Japanese Denim

After Japan’s defeat in the Pacific War, the country faced severe material shortages. In 1951, Mr. Tetsuo Oishi (大石哲夫), the son of the founder of Oishi Trading Co., then working at Hitachi, was asked by a politician to take on a special assignment. Because his father had been in the used clothing trade, Tetsuo was sent to the United States to import secondhand American clothing into Japan.

It was during this time that he first encountered blue jeans. He noticed that many Americans wore them in a way that was remarkably clean and stylish. The jeans were in vivid blue. Even as secondhand items, they carried an undeniable appeal.

Alongside general used clothing, Oishi began importing around 30,000 pairs of Levi’s 501 jeans each month. Sold in postwar markets like Ameyoko and Yokohama, the jeans passed through multiple markups—retailers priced them at nearly 4 times wholesale—yet they still sold out instantly. Tetsuo Oishi became wealthy almost overnight.

This success sparked a new idea in Tetsuo: if used jeans were this popular, how incredible would brand-new ones be? Motivated by this thought, Tetsuo began studying how Levi’s 501s were made. He discovered that the fabric came from Cone Mills and the sewing was done on Union Special machines. After about a year of development, he created a prototype.

Tetsuo then traveled to New York to propose a partnership with Cone Mills. However, Cone Mills declined instantly as at the time they supplied their coveted 686 denim exclusively to Levi’s. Undeterred, Oishi searched for a denim equivalent to Cone denim and found it at Canton Mills in Canton, New York. This discovery led to the launch of CANTON, the very first authentic Japanese jeans brand. It became a massive hit in Japan, and huge jeans factories were built in Miyagi and Akita Prefectures — but they still couldn’t keep up with demand.

Looking for more production capacity, Oishi discovered that Kojima in Okayama was a major production hub for school uniforms in Japan. He realized that those factories were capable of sewing thick denim, and began working with Kotaro Ozaki, a uniform maker at the time, training them to produce jeans as a subcontractor for CANTON.

Kojima, the Sacred Land of Jeans

Maruo Clothing (or Maruo Hifuku) factory ran by Kotaro Ozaki eventually evolved into BIG JOHN and became the number one brand at the time. From there, most of the factories in the Kojima region shifted from school uniforms to jeans production. Many launched their own brands, and Kojima became known as the birthplace of Japanese denim. Over time, Kojima has gained its popularity as “Sacred Land of Jeans”.

Due to this history wave, some publishers misunderstood the history and had given the misleading impression that Kojima was the birthplace of Japanese denim. There’s no doubt that CANTON was Japan’s first true jeans brand to produce a 14oz indigo blue jeans that could rival Levi’s 501 at the time. But sadly, it was eventually overshadowed by the rising brands in the Kojima area and faded into the background.

All in all, the credit of the first Japanese jeans brand should be given to the CANTON brand whose jeans were made in Miyagi and Akita Prefectures.

The First Japanese Jeans in History

As we dig deeper into the history. We discovered that the first Japanese jeans were actually made by Takasaka Sewing Machine Company in Isesaki, Gunma Prefecture—a distributor of UNION SPECIAL sewing machines. They converted a warehouse into a sewing factory, where Mr. and Mrs. Watanabe sewed the jeans at. The Watanabe couple were hired by Tetsuo Oishi to produce a pair of jeans that could not only rival but superior to the 501. After ten months of development, the true first Japanese jeans were born.

The Father of Japanese Jeans

In short, it was Tetsuo Oishi who was the true pioneer of Japanese jeans. As Masao Oishi recalls, “Mr. Oishi admired Konosuke Matsushita, the founder of Panasonic, as a man of great vision. He taught me many philosophies and treated me like a son. He was a 6th-Dan in judo under Jigoro Kano at the Kodokan. There’s even a story of him throwing a yakuza over his shoulder in Ameyoko (laughs). He was considered big for his age, weighing around 100 kg. Definitely a strong man. at the time.”

The History of ONI Denim & Mr. Oishi

We started our journey to blog on denim culture about 15 years ago. Blue Beach Denim has since been the center of raw jeans and classic menswear in Taipei. As a later comer to the Japanese denim world. We’re lucky enough to connect with some of the best craftsmen in Japan. Many have become good friends and are an inevitable part of our success. Before seeing it in person. ONI Denim wasn't really the one denim brand that I feel I have to have. But after years of experience in brand selection and curation. ONI keeps coming back to my view and raises my interest again and again. From their “Secret Denim” to the natural indigo dark blue denim to the unprecedented “Asphalt Denim” and the more recent groundbreaking work of “Crushed Concrete Denim”. They all surprised me in ways that other brands failed to do.

How Good Is ONI Denim?

There’re 2 reasons that separate ONI from others. One is the constantly innovating denim fabric. As a veteran in fabric design, Oishi-san basically understands the Japanese denim industry inside out from his experience with vintage Levi’s fabric to heritage Japanese denim to mass produced wide loom denim. This grants him the knowledge to go beyond the border of the known world of denim. They’re all secret recipes that cannot be reproduced by others. Second is the unparalleled fits. As a master in the jeans production planning, Oishi-san excels at making clean fits out of unsanforized denim, which is a real challenge to any designer. This process not only takes extra sampling but also requires extensive experience to reach the sweet spot. These are the two qualities I look for in any brand: it has to look good, and it has to feel good. Only then will you truly want to wear it every day. ONI being one of the top denim brands on the chart and as my personal favorite. I decided to share my understanding of the brand and hopefully shed some light on the rarity and the true craft behind this secretive one-man-brand.

What Is ONI Denim and What’s So Secret About It?

ONI Denim was founded in 2001, it is run by one man who is now 76 years old (this year in 2026). ONI has no website, no contact, no distributor, and no advertising. Instead, it has grown purely through word of mouth. The origin of the name "ONI Denim" traces back to the brand's first business visit to retailers in Tokyo. The distinctive texture of the first ONI jeans sample left a strong impression on the shop owner. The hand feel was so irregular that it was compared to the rugged face of a devil ("oni" being the Japanese word for devil). And from this story the name ONI Denim was born. To carry ONI, a retailer must share the brand’s values; only the very best and most aligned shops are chosen. The philosophy is simple: the product speaks for itself. Because of this, many consider ONI Denim one of the most secretive denim brands in the world. It exists in a rare contradiction: highly elusive, yet at the same time widely admired and sought after by many.

Masao Oishi (大石正夫), the Mastermind Behind It All

The founder of ONI Denim. Before then he spent 35 years in the Japan jeans industry. He worked under Tetsuo Oishi at Oishi Trading Company for 20 years before starting ONI Denim. Many mistaken Masao Oishi as the son of Tetsuo Oishi, but actually they just happened to share the same family name.

The Background of Masao Oishi

In early 1970s, Mr Oishi-san joined as the first cohort at Levi’s Japan and worked there for four years before starting his own apparel business. It was a women's casual pants company where he had continued success of releasing hit products in Harajuku and Shibuya,Tokyo.

“But later, authentic French designer jeans SASOON appeared — it is what we would now call something like a “designer brand”. And with only small factories and small fabric suppliers, we couldn’t keep up with the competition. That’s when I decided to join Oishi Trading, a move I had already been invited to consider years before.”

In 1979, he was headhunted by Oishi Trading (unrelated to Mr. Tetsuo Oishi, despite sharing the same name). The company was struggling after the CANTON era, and Masao was tasked with helping to turn it around. Soon after joining Oishi Trading Co., Masao developed numerous hit products, the most notable being the Pedal Pusher Jeans, which became a breakthrough success for the company. Unfortunately, other large Japanese corporations copied the design for wholesale. With their far greater scale, those pants sold over 10 million pairs—a well-known episode from that period.

During his time at Oishi Trading Co., Masao gained experience producing both men’s and women’s jeans across a wide range of price points and production scales. He became an expert in pattern making for both, as well as in the production of raw and washed denim. At the time, Masao was using Cone Mills denim. But later he was introduced to Kuroki by Toyoshima, a major textile trading firm. Back then, Kuroki was in financial difficulty, and its current president was only a managing director. Masao selected a few of their fabrics, turned them into products and they became major hits on the market. This success helped Kuroki recover. And because of that, the president has trusted Masao Oishi ever since.

That trust is why Kuroki continues to fully support the production of ONI Denim, which is made by a single craftsman. In recent years, Masao even helped broker a partnership between Kuroki and LVMH’s “Métiers d’Art” project, making Kuroki the only Japanese textile company to enter such a collaboration—a milestone that attracted significant media attention. Kuroki is producing by far one of the most coveted denim collections in the world. We’re lucky enough to have the chance to travel there this September to peek inside the mill operation.

A Trip to Kuroki with Blue Beach Denim

After working with ONI for several years, I’ve come to realize that many of the fits and fabrics popular today were already created and had success long ago during the era of Oishi Trading. Building on those history and lessons, ONI continues to refine and push its craft every single day, one denim at a time. I guess this persistence is nothing short of a true legacy of Japan. And maybe the luckiest person is me, who now gets to enjoy these works of art everyday. See for yourself here.

P.S.

The photos of the magazine were about Tetsuo Oishi and Oishi Trading Company. He was quite popular back then with visions of international business. Masao Oishi was menteioned in one of the many pages. And later on featured in many other publications as he succeeded in his career. After all those glamorous years, he decided to stay behind the scenes when he started ONI Denim.