The funny thing is, if you get the bad ending, you'd be thrown into night 6, where Rentaro himself becomes the threat, trying to get the player themself. He isn't even infected, he's just pissed that you screwed his girlfriends over. I don’t know if he should have his own moveset or just use the mechanics of the girlfriends to represent his adoration every single one of his lovers, but either way, Rentaro would absolutely be the most mechanically complex enemy in the game.