Domesticity is so specific to the couple in question, I think. Like yeah, “cuddling in bed” is such a nice domestic trope but I feel like there’s another layer people tend to miss.
Like, Dazai and Chuuya go about their normal routines even on their days off. Chuuya gets up and goes for his run, while Dazai isn’t even up until after Chuuya has been back for a while. They get their morning coffee together, maybe eat some breakfast, but then go about their days separately. Chuuya might work from his laptop, at his desk, while Dazai reads a book on the couch. Dazai will watch TV in their living room, and Chuuya will be doing the dishes in the kitchen. Chuuya pours himself a glass of wine in the evening and brings a drink to Dazai even though he didn’t ask. They silently communicate through most of their day, like they do in their partnership. They’re so used to each other that it’s just second-nature.
Ranpo and Edgar spend their evenings competitively watching crime dramas from everywhere in the world, trying to see who can solve it the fastest, and watching to the end to find out. They bake sweets together, and Ranpo sneaks Karl some snacks (much to Edgar’s annoyance). Ranpo plays his switch while Edgar writes, and maybe they switch places after a while, so Ed can navigate his way through the game and Ranpo can read. They go to bed early, and Edgar stays up a little longer, invested in some book he can’t put down, or jotting down his most recent ideas. Ranpo wakes up earlier than the other and heads into work, but makes sure Karl has been fed and taken care of beforehand, so his partner can rest a little longer. They’re the old sappy, in love couple at the supermarket or in the park, going about their weekly routine without a care in the world for anyone else around them.
Akutagawa and Atsushi, both of which grew up with scarce amounts of food, will share their meals and snacks, always allowing the other to take what they want from their portion. They go on the weekly shopping trips with Gin and Kyouka. They clean together and clip coupons out of habit, they spend their weekends playing cards in the laundromat, waiting for their stuff to be done. Atsushi brings him some food if he’s working late, or they meet up for lunch during the day. Atsushi coaxes Akutagawa into being a little more social, and in turn, Akutagawa’s realism starts to rub off on Atsushi. They argue, sometimes, but that’s because they’re still growing as people, and trying to figure out how to grow together.
Idk, I like to think about how each one of these couples fits together and is just comfortable around each other and comfortable sharing a space together, even if they’re not doing anything actually together.