From what I understood, it's just how it started and not the whole reason. Anyway, the whole thing is weird so I don't really think it was meant to have a lot sense to begin with. :x
From what I can tell they tried to have sex, but then it didn't work out so the dude blew up on Ken coz of his insecurities
ohhh okay yeah that makes more sense, still a wild ass reason author def just used it as an excuse for smut
This makes me realize that dude could have just told his past self to not overreact like that and call it a day
frrr why was his gut reaction to fuck his younger self instead of just talking to him and reassuring his younger self that it doesn't matter if it takes a few times for penetration to go smoothly.
thats such a stupid ass reason to break up, just because his ass was too tight? seriously?