Turns out the sensei is on a revenge quest and all her victims are really the victims of her father and his shady patter, or her toys already had problems of their own and she helps them with their dark tendencies;since she herself is broken that help take on a s*xually sadistic form. This way our MC's become likable. Though I think story could have worked with them being outright antagonists.
The main guy is the only guy we get to know, that's good thing, he has his harem of broken women and he himself is broken up in a way that tragic. He just does not feel happy or sad for himself, this passive character does what his told but not in a annoying way. The true victim here is shiruza yukino who is being used as a tool for revenge; but even this is put into new light when we find out her father has raped and is planning to rape his daughters!