ONI's Secret Denim is legendary among denim enthusiasts for its unparalleled texture, softness, and character. For the last few seasons, this iconic fabric has been available in a stunning double-black version — combining the rugged charm of its indigo counterpart with the deep intensity of sulfur-dyed black. The fabric is consistently sold out, as only one workshop in Japan still performs sulfur dyeing for yarn this heavy. Production is extremely limited, and units always sell quickly — this version may become a true collector's piece, as the workshop responsible for ONI's sulfur dyeing will soon close its doors.

First introduced in 2012, Secret Denim has been meticulously crafted by Oishi-san using an exclusive process that no one else can replicate. Extra-thick yarns made from three types of cotton are woven at ultra-low tension on vintage shuttle looms, resulting in a 20oz unsanforized fabric with incredible slub, roughness, and a uniquely hairy, woolly texture. For this black iteration, both the warp and weft are sulfur-dyed, achieving a depth of color that is as striking as it is versatile.

The silhouette is ONI's 288 regular straight fit — a straight leg design with a medium-to-high rise and a slight taper from the knee down. The cut offers ample room through the seat and thigh, blending comfort with style for an easy, refined profile that works equally well with boots or sneakers.

Construction details continue ONI's quiet obsession with refinement. The jeans feature ONI custom black enamel-coated steel buttons, black powder-coated copper rivets, hidden back pocket rivets, heavy-duty bar tacks, durable cotton-lined front pocket bags, a peek-a-boo selvedge coin pocket, raised belt loops, and a custom vegetable-tanned deerskin leather patch with the ONI logo.

Fit Notes: This model fits true to size for ONI — the tagged size closely matches the actual waist measurement. Compared to most global American brands, sizing is similar or slightly smaller, so you may take the same size or one size up. The denim is unsanforized but has been one-washed, so no further shrinkage is expected. With regular wear, the waistband will stretch approximately 1 inch, allowing the fit to settle comfortably over time. We don't recommend sizing down, as starting too tight may cause discomfort and alter the intended fit of the garment. As always, we strongly recommend checking our size chart to find your perfect size.

Visit our LOOKBOOK and discover a great selection of heritage street-style outfits

• 20oz unsanforized black sulfur-dyed Japanese selvedge denim — one-washed, no shrinkage expected
‎• 100% cotton
‎• Warp: black / Weft: black
‎• Extra-thick yarns from three types of cotton
‎• Woven on vintage shuttle looms at ultra-low tension
‎• Slubby, woolly, hairy texture
‎• Regular straight fit (288) with slight taper below the knee
‎• Medium-to-high rise
‎• Red selvedge ID
‎• ONI custom black enamel-coated steel buttons
‎• Black powder-coated copper rivets
‎• Hidden back pocket rivets
‎• Heavy-duty bar tacks
‎• Cotton-lined front pocket bags
‎• Peek-a-boo selvedge coin pocket
‎• Raised belt loops
‎• Vegetable-tanned deerskin leather patch with ONI logo
‎• Super limited quantities
‎• Made in Japan

Spain

FREE SHIPPING on orders over 100 EUR .

6 EUR shipping cost on orders under the value mentioned above.

European Union & The UK

FREE SHIPPING on orders over 150 EUR \\.

14 EUR shipping cost on orders under the value mentioned above.

Rest of the World

FREE SHIPPING on orders over 250 EUR .

25 EUR shipping cost on orders under the value mentioned above.

If for some reason you are not happy with your purchase you can return it to us within 14 days for a size exchange or refund.

For more info please visit our returns & exchange page.

Please note that items in the SALE category are considered FINAL SALE, with no returns or exchanges accepted.