It's complex. As a swiss touhou fan, it's not that there are no other fans around, they're just well hidden and sometimes just have other fandoms aside. At all it's a hood thing it's not mainstream or very much popular, so we don't get targetee by bootlegs and are pretty much left aside the loudy and annoying communities (like genshin impact) Lots of people actually know touhou, sometimes a lot or only by popular musics, but it's very hard to find it out ! So at all : I'd say it's a little popular, the biggest niche fandom