It's 100% willpower. MC is the only sane person person in this manga.This fucking herbivore ISTG, one of you guys isekai into him and improve this manga asap.
It's not willpower it's cowardice
Besides, if he ever does do anything it's going to be with Shinozaki-sensei. People may not want to admit it, but she's being framed as the "main girl."