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 trending 200 fit — a high-rise, wide-leg cut perfect for those who appreciate a vintage-inspired style. This profile combines a roomy, easy fit with a classic shape, offering both comfort and a nod to timeless denim aesthetics. The result is a jean that wears with relaxed confidence and pairs effortlessly with boots, sneakers, or sandals.

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.