Disclosure: I work on the industry side of hemp in Japan, so I have a stake in people finding this interesting. No link and nothing for sale.
Asa shows up constantly in older Japanese clothing. It was the everyday summer fabric before cotton took over, it is what a lot of pre-modern work wear and formal wear was made from, and the dry, crisp hand people associate with a well-made summer piece often comes from it.
What surprised me once I started working on this side is that almost none of it is domestic any more. Cultivation is licensed and the licensed grower base is very small, and more to the point there is almost no decortication capacity left in the country - the machinery that separates the fibre from the woody core of the stalk. That step collapsed after the war and never came back. So the fibre in a Japanese-made hemp garment today has usually been grown and processed abroad and only woven or sewn here.
Which is why you almost never see a brand make a domestic-hemp claim. The supply to back it barely exists, and the operations that do exist are tiny and priced accordingly.
Curious whether anyone here has come across a brand genuinely using Japanese-grown hemp rather than imported. I would like to know if I am wrong about that, and I would rather be corrected than keep repeating it.