Ok, he's trash. Like serious trash. Until now we saw him with several other girls, but I naively thought they were his side chicks already before Yoshino showed up, but him chasing other girls while he says he loves her... he is probably narcissistic psycho or something like that.
And the age gap wasn't that bad. It's around a three year gap. She was 18 as a freshman at the youngest, and it's been three years since they met. So he was 14-15 at the time, but the dude lost his virginity at 12... and it's usually the other way around. College guy with junior/high school girl. As long as it's not something like 18 y/o with 10 y/o (basically where one side is too naive and can be easily tricked) then I find it to be whatever.