Because he doesn't feel that way about her? Which he has made clear since the beginning of her relationship. But despite that she forces him into a relationship he doesn't want by blackmailing him and threatening his family life. I know its fun to fantasize about a cute girl loving you unconditionally, but she has some serious issues with boundaries, and if the methods she uses to get into a relationship are that toxic, imagine trying to actually be in a relationship with her. Personally, I'd choose the girl with more personality traits besides just "mc makes heart go brr". You know, the one with actual aspirations for her career, has her own passions and dreams that she doesn't unload out people, someone that won't break down crying like a fucking toddler in the street if she doesn't get her way.