It has only been TWO days since she made any active attempts to improve his life.
And it's been however long since he's dissimulated with her a friendship that was life-savingly beneficial for her, not making it clear he intractably resented her for whatever actions against him while she constantly brought up her remorse by herself.
Those were saving him from a suicide attempt (something he himself was planning on doing since the beginning), and bringing him out on a single date which SHE insisted he should go to.
So, you're saying she
saved his life, and then resolved to actively repay the kindness he showed her (pretense notwithstanding), after however much time he spent dissimulating friendship.
Joining in on the bullying doesn't make it HIS revenge though.
If his revenge was a person, it would have severe congenital neurobiological deficiencies. This guy doesn't get to have revenge plans.
Also cops? Going to the cops when society is more likely to favour a female victim
No, stop that-- she had
video evidence of her crimes, since she made the videos as part of his humiliation. That's not just assault, that's CP. Prosecution would be
trivially easy, especially at the start of this story, not least of all because she'd probably have just accepted it as her comeuppance by chapter 1. Literally, the only justification you can give is the meta-explanation of "the police in manga are generally only useful inasmuch as they're an obstacle for the protagonist".
He was already suicidal. His sole reason to live WAS to kill himself in order to hurt her.
For one thing, chapter 15.1's title is "It's not like I wanna kill myself over my suffering", so that's not correct.
Second: suicide was not the original plan, which is why revenge is talked about in every chapter title with no reference to suicide until chapter 13, titled "I wonder whether you'd suffer more if I died". In fact, we don't even know what the plan originally was beyond him betraying her after he sufficiently ingratiated himself with her. Suicide became the plan after he got the shoes beat off him by the girl's bullies, and he saw how distraught she was because he got A) bullied B) because of
her. Then he figured, "I can make her feel bad by killing myself!"
But how did he plan to enjoy his revenge after making himself dead as hell?
I'm not saying he has to forgive her-- I'm not even saying he shouldn't have a revenge plot. But he's already dissimulated forgiveness for someone that's incessantly remorseful for her past actions, and has granted her companionship and dependency on top of that. He has willingly and actively associated, and spent time on, and taken out to
dates (plural), this woman who sexually assaulted and humiliated him. This presumably has caused him continued anguish, except
this time, he's proactively invited that anguish onto himself.
This is just
inefficient. Incoherent, even.
Kid should have just got a gun
-- or shot her with a kyuudou arrow, or something, since it'd be difficult to get a gun in Japan.