i have seen some manhwas actually directly showing douching (or having characters mention doing it). can't name any from the top of my head because I have terribile memory, tho.
I'm guessing most authors don't like to talk about douching because it's a "turn off". Personally, i don't think good prep and hygiene are turn offs, but imagine you're a writer/author and you're trying to *turn on* your audience with a sex scene: you don't want to talk about poop and cleaning your intestines, because that would be a turn off.
this changes if you're trying to tell a realistic scene. in that case, talk about douching could fit a lot better and naturally ^^
I remember reading one where they met in a bar and then went to top's house to fuck and the bottom was like "wait I was expecting to get laid today so didn't clean my ass, gimme a moment I'll douche my hole" and the top was like "nah I ain't getting out, I'm doing it for ya"
So that's my only exposure to ass cleaning lol
I might be thinking too deep into the technicalities here but do these BL ukes ever douche before getting their asses eaten and tongue fucked? (Like clean their rectums from insideout) cause I swear half of these bottoms be working and sweating all day, they don't even get the chance to shower or douche and suddenly their tops be sucking their assholes like it's the most tasty delicacy they've ever eaten. Do these tops have no gag reflex at all? Do they love the taste of shit or do these ukes just have magical assholes that are always shit-free and smell like sunshine and rainbows 24/7. I think I need to shut my brain off while reading Yaoi cause Yaoi has its own logic about sex that's far from reality, but being the clean freak that I am I just can't help wondering about the hygienic aspect of it all.