We got to give the kid credit thou hes smart enough to see a good thing for what it is and roll with it early, most guys are far too stubborn or dumb at that age to understand how much of a win a girl like Mana is, we give her flowers for locking in early but the fact he didn't actually ever reject her advances and rolled with her personality is entirely to his credit.
Makes me wish more MCs were like him, romance mangas would be far more enjoyable to read if some guys just accepted that they have a good thing going and not actively try to sabotage themselves.