Comment by Бобряк Рори on 29-Sai Dokushin Wa Isekai De Jiyuu Ni Ikita……katta - Chapter 21

If you haven't read the original, which the manga is based on, let me explain. In the novel, Taichi, in a fit of rage, brutally tortured and ra**d her right there in the forest. She was a virgin. So he feels guilty about it.