The first time I read it and went through the setting, I thought this manga was interesting and really got something special about it. Now it just seems bleh, this plot with the short-haired girl sacrified for the asshole is such an asspull and has litterally no reason at all. Why she likes the dickhead so much anyway? Sex? That's insulting. This happens just to make the reader go emotional I guess.
i wouldnt go as far as calling it an ass pull; abusive relationships are a real thing, which is what is going on there. she is most likely suffering from battered person syndrome. hell, its so much of a thing, Family Guy has an entire episode about it. an episode that was critically panned for being too serious, too depressing, and for going so far that it couldnt be called satire.
and how is her liking him because of sex insulting? sex is both a physical and mental thing. he makes her feel good both physically and emotionally (however, the same cant be said for kazuya, who does not feel anything except for his obsession with anna). she also bonded with kazuya over the death of the boy that liked her. these strong emotions coupled with her young age (remember, she is still a child) make it believable that she would develop an intense attachment to kazuya, regardless of whether or not it is healthy for her. thats why its so easy for kazuya to manipulate her.
The author seems to just want to awe his/her reader rather than give some realism or just some freaking logic to his/her story and character. It might get better? But with this over the top stupidly evil dickhead and this sorry excuse of a supposedly dark emotional moment? I don't think it will. There are too many anime, manga with edgy ridiculous trash already. Well, waste of potential, waste of time, dropped.
i wouldnt say it isnt realistic or logical either. kazuya before the going back was ridiculed, bullied, he was depressed and had low self esteem; he was already a ticking time bomb. his fuse was irreversibly lit when he got his classmate killed in the car accident. after that, he kept on escalating his actions. its very much like how people start off with torturing/killing small insects and escalate from there. every time he does something evil, he loses more of what little humanity he has left. so while kazuya's actions seem illogical, they stem from a logical catalyst.
getting away with evil makes it easier to do evil. similarly, causing death makes it easier to cause death.