I mentioned this in a post about "unwoke Japan", so here's the evidence. There is at least one dojinshi bookstore in Japan that has a section organized by the character who is bottoming.

The labels have the character's name followed by 受 (uke), which means being the receptive or passive partner, or in BL slang means the bottom. Most underrated organizational system ever by the way. Please show this to anyone who claims that "unwoke" Japan doesn't "shoehorn queerness into everything".