He is kind of a broken person due to his past, so it makes some sense he can be quite blind to many things. When he was himself never loved, it can be hard for him to know how to love. He's an idol, so the work forces him to act cordially if not friendly and look happy, no matter what, masking his flaws. Furthermore, the idol and show business world is full of fake love, so when you are a person who doesn't know what love is, it might be confusing.