We have Akai Asahi, who has the lowest grades in the school and is traditionally attractive and emotionally bursting. And we have Konno Mitsuki, who has the highest grades in the school and is frumpy and cyborgial. These extreme opposites are what create interest in the couple since it's two people you wouldn't normally expect to be together (even though the relationship is based on her bribing him to temporarily date her). After spending an oddly short amount of time with her, Asahi is able to recognize Mitsuki's subtle emotional expressions and it ends up being something special between them, where he can understand her personality even though other people can't. Likewise, if Mitsuki hadn't gotten a makeover, the story could've included the idea of Asahi recognizing what makes her beautiful even though to everyone else she looks drab. But noooo, the author missed that opportunity and just had to give her a makeover so she'd be traditionally attractive as a leading lady.