Responses
Because that is how abusers work. They make their victims believe it is their own fault and not the abusers. It is a vicious cycle and hard to break. Mitsuru lucked out in the fact that he managed to get his abuser to break it off without getting killed.
It's so sad that Mitsuru blames HIMSELF for Kouichi abusing him. "Oh no no he didn't burn me, well he did but..." WTF?!
Also bless Shougo for his big heart - not everyone will be able to accept someone again after such a thing (even being crazy in love with them).