was making myself sad with fic plot ideas that will never come out as a proper fic, so here, have a chunk of text of what could have been a fic
osomatsu and osoko are great drinking buddies, and they fool around often, but they both know that nothing will come out of it, because he’s not responsible at all and thats not what she wants.
oso n kara hang out one day and she bumps into them by chance. and osoko is immediately enamored by karamatsu. (in which osomatsu is bewildered because she calls him handsome and oso is like “um???? we have the same face????”) and kara is loving the attention and they flirt and oso is like, wtf ur both crazy im out
so karamatsu and osoko actually hit it off and they end up dating. and nobody really cares because “haha she must be nuts if shes going out with kara and likes it” and oso is feeling this nagging in the back of his chest and he doesn’t understand why because he didn’t feel that kind of jealousy when jushi was going out with that cute girl.
karamatsu and osoko are super cute together and even the brothers hate to admit that they dont mind seeing karamatsu happy. osoko is pretty neat, not super flashy and she cna hold her own against them.
so one day while oso is brooding on the roof, kara brings osoko back, thinking that no one is around, they decide to have sex. and osomatsu is like super pissed off because hey, wtf, i sit on that couch. he can see them from the patio window if he looks over, and he cant help but watch them, because, hey, live porn. and if he listens closely he can hear them, and his mind starts thinking that karamatsu is calling out his name and woops, kara makes eye contact with him at that moment. embarrassed that he got caught, osomatsu crawls out of sight and jacks off on the roof. (*insert infamous ""im so fucked up" shinji ikari quote here*)
after that, karamatsu hasnt really been able to look at osomatsu straight in the eyes. not that osomatsu knows why because /he/ was the one that jerked off to the sound of his brother, not that other way around.
kara's been spending less and less time at home, since he's been staying over at osoko's place. osomatsu brings up his irritation with the couple to his brothers and they're all "eh, well, what can we do about it." and to which ichi laughs and says "what, do you have feelings for kusomatsu or something" and oso is all "Wtf im not a homo, get out of here", to which ichi is like "im joking" and they all resume whatever the hell they're doing while oso kinda pretends what ichi said didnt bother him as much as it actually did.
osoko calls him out to have a drink with her one night. he meets with her, and she tells him that kara's been kinda down in the dumps lately, and she wanted to ask if he knew anyhting about it. and osomatsu gets kinda angry, like, hey, hes been over at your place lately, maybe he doesn't want to be around you and thats why he's like that. and osoko gets offended but osomatsu apologizes because he knows that's definitely not true. and she hints that maybe kara misses his older brother and osomatsu kinda snorts but his heart did something weird, might need to go to the doctors soon. so they talk about random stuff, and she kinda hints that maybe she would invite him to bed, like, with karamatsu, and like, osomatsu had never been invited to a threesome, heck yeah, lets do it.
the next time oso sees kara, theyre naked and the only thing in between them is an equally naked osoko. and you would think that since its been a while since he'd had sex (obvs he only ever did it with osoko, and never when she was with karamatsu. oso's not that big of a dickhead.) that osomatsu would actually focus on the boobies in front of him but for some reason he cant stop staring at the way karamatsus lips skim across osokos skin. and when karamatsu looks over its like hes looking straight at him, like he wants something. they never end up touching at all, despite the not so large bed and the medium sized osoko.