Adolescence
Everyone says that he has double personality but genuinely I think he's just a awful human being that seek for woman validation because he's self insecure but at the same time he believes that woman are no better than man. It gets more clear to see in the 3th episode, when he keeps asking the therapist if she like him even a bit but during all the episode he keeps screaming, getting angry and scaring the therapist.
When we think about the girl he killed we see a girl that had her nudes being exposed for her whole school and then a random guy ask her a out and she rejected him, he starts getting angry and a time after he gets angry enough about it and kills her.
It's clear that he killed her because she rejected him and not because she bullied him in the 3th episoden when he gets mad at the therapist so the guard shows up and he gets scared of the guard, the therapist signals the guard away and the guard does making the boy get angry about how she was on control.
And of course the action on every single episode EAT, absolute awesome actors. In special the principal actor and the therapist, the 3th episode being recorded all at once with no second takes or pauses just proves how awesome actor and actress they are.