I'm all for resurrecting the Teacher, just so he can die again 😶
Kinda interesting to see the usual revenge scheme reversed, rather than having the actual kill as goal for closure, all of this plays out knowing he's already dead and mc did his time for it and is now processing the event, though i wouldn't have needed to see the actual scene 🥲
Yeah this is why the manga's interesting, because it's a theme we usually don't see in manga: that vengeance is hollow. His sister's still dead, and all he has is the understanding that he killed someone's father along with the fact that he couldn't save his sister. Even if the manga has gone out of its way to show that he was perfectly justified and actually did the undeniably right thing(he was abusing his own children, too, which isn't that much of a turn for a violent sex offender), it doesn't bring anyone back or repair the damage already done.
Violence hurting those who do it feels rare in manga, and its a point here. The girl who stabbed the insane boy on accident also felt distraught, even though she was totally in the right, didn't even mean to do it, and the kid lived. But she still felt guilty about harming another human being, something that normal human beings all feel.