that's a difficult question. they're versatile in tropes they can pull off well thematically. I do like writing or thinking of them sharing a bed, where it's new and odd at first, then they grow used to it, then can't live without it. basic in terms of what romantic ships do, but it's a classic for a reason.

one thing I think they'd do, no matter the universe, is sobbing or having a mental breakdown in the other one's arms. this is part of moments they and only they get to see. like an inner world where only the two are allowed. it's new to them to have someone there when they're at their lowest. scary and oddly comforting. I can't tell if it's my actual favorite kndz trope, or if it's widespread, as I don't read a lot of fic these days.

I don't see a lot of talk, however, on kunikida getting the occasional scolding/behavior callout. this man is far from perfect and knows it. and it's actually good for him to have a rude awakening on occasion. at a first glance, it seems like dazai has no leg to stand on in regard to telling someone off. sometimes he is right, kuni is wrong, and dazai develops the guts and the intimacy to say so. this for sure I'd like to see addressed more often.