@Tearsax Dude, the girl literally says that Harumi dumped him. That has no other possible meaning, either inside or outside context. People only "dump" people when they are dating. It can't get anymore explicit than that. When the plain sense of the text makes perfect sense, seek no other sense. What he said about falling in love makes perfect sense only if you understand that they dated. Just because they dated doesn't mean they fell in love. The relationship probably ended before they could sort out their feelings. And think about it; why would he say they
could have fallen in love if they never dated in the first place? It also explains why he can't see her as his mother; you probably would have that problem too in his situation if your "mother" was someone you dated. Because of Japanese culture, he has to see her as his "mom" despite their past. It's no different from this manwha, really, where the stepmom is trying really hard to be seen as mom, even though she's not much older than her "son".