Chashin (茶芯) is a leather term before it is a denim one. The first character means tea, and by extension brown; the second means core. It describes hides tanned brown and finished black, where the surface wears back over the years to show the brown underneath. Pure Blue Japan has been translating that idea into cotton with its TCD series, and the TCD-005-BR brings the 2026 version, Teacore Black x Brown, to the brand's slim straight cut.

The warp is dyed brown first and then overdyed black, so every yarn carries a brown core under its black surface. Where the earlier teacore release paired that warp with a black weft, this fabric switches to a brown weft, which warms the black slightly from the first wear and shows at the cuff when rolled. Woven to 14.5oz from Pure Blue Japan's characteristically uneven slub yarns on shuttle looms, the denim is unsanforized and one-washed: the bulk of the shrinkage has been taken out, the hand is already slightly broken in, and the surface keeps the texture the brand is known for.

The fade follows the leather logic. Knees, thighs, seams and pocket edges lose their black coat first and turn tobacco brown, while the slub pulls that contrast into vertical streaks. Over a long wear cycle the whole pair drifts from dense black towards tea brown rather than the gray of a standard black denim.

The slim straight cut sits at a mid rise, slightly slim through the seat and thigh, then close to straight from the knee down to a 7.5" leg opening.

Hardware stays tonal: a five-button fly with black-coated buttons, black-coated rivets, black pocket bags, a black lambskin leather patch at the back waist and the Pure Blue Japan leaf logo embroidered in black on the back right pocket. The single note of color is the brand's blue selvedge ID, visible when cuffed. Made in Japan.

Fit Notes: Pure Blue Japan sizes usually run a bit small compared to most global American brands. The waist measurement typically matches the tagged size, without the extra inch most American labels build in. We recommend taking your usual size, or going one size up if you prefer a bit more comfort. The denim is unsanforized and one-washed, so the main shrinkage is already done; expect a snug start that stretches at the waist with wear (up to 1"), and wash cold to limit further shrinkage. As always, we strongly recommend checking our size chart and comparing it with your best-fitting garment to ensure the right fit.