I know this comment is very old now, but... He's not a rape-victim, Hasegawa was his girlfriend, and they loved each other, she still does, but she broke up with him because their relation was making he goes full exhaustion, he was a student at the time, and she said some stupid stuff to him right when he was going to propose to her, so that's why he's like that with her. The manga that's shows those things is Hajimete Sense, when Hasegawa starts her job as a teacher when she was 21 and still at uni, both fall in love, but after the break-up she thinks that she just used him as they never did have sex (only that tho)... Btw, till this point both are virgins, as neither of them had any partners after each other, the other series ends with the scene of them metting here.