You were close with both of the twins, moreso Atsumu, Atsumu was very chaotic when comfortable and you sure as hell were the one he was most comfortable with, you were almost constantly over at his house and just chatting away or doing whatever, staying over and watching movies with the twins, Osamu cooking while you chatted and Atsumu listened, it was fun and a pretty good vibe, it meant Atsumu didn't care about things like getting changed, or anything, ever, so when you were in the shower in the home of the Miya twins, it probably shouldn't have shocked you when Atsumu came in, probably to piss or something along those lines

"Ya havin a good shower?" Atsumu asks casually, his accent still rings nicely in your ears