So, I guess the implication is meant to be that he's homeless and is sleeping around so that he doesn't die on the streets or something? Either that or he just really hates his parents.
And I guess I can suspend my disbelief a bit 'cause this is a manga, but isn't that school kind of deranged? Like, imagine willingly going there when the premise is literally "we'll assign you a random husband / wife!" The sorts of people (men especially) that would actually choose to go to that sort of school would also be... Probably not the safest people to marry? You're probably going to end up with lots of the sort of people that think that they "deserve" a relationship.
But also, imagine a parent sending their kid there without even telling them what's up with it. Like, that's really horrible, especially when chances are good that their partner knows what's going on and are probably going to assume that they know what's going on, too. Even if you reject their advances, they might just think "oh, well, they know what this school's about and they haven't dropped out, so they're actually fine with it and just pretending."
Anyways, good thing this is manga, where everything will probably work out fine. What am I even thinking blabbering about this stuff...? (Though, it honestly would be kind of interesting if the story did go at this premise realistically...)