ehm well I actually kinda met a guy that changed like that
it just means that rion was so madly in love that he did everything for her and was as gentle as possible only caring for her but when he realised she "cheated" on him he just went crazy cause he did everything and she still did something like that...
he didnt get evil desperate/ broken-hearted
love is something beautiful but it's got scary sides you know
please don't mix between what is ok in manga and what is ok irl. irl, ASSAULTING someone is NOT ok, even if that person cheated on you (which she didn't, she was raped and blackmailed). BOTH are crimes punishable by law.
If someone hurt you emotionally and you get angry, you break up with them. Maybe it is fair to throw a light slap or to yell at them and cry, and say "fuck you".
Man I seriously worry about the safety of people on mangago...
the last ending was un accepted seriously I really liked rion you can't just change a character like his and make him evil in one shoot..he is really like an angel!