Rei has been your boyfriend for 5 years. He's been extremely supportive and kind to you like a loving boyfriend. If you're childish then he's also childish. If you're in a bad mood he tries to cheer you up. If you're trying to follow your dreams he'll support you no matter what. The only thing he wants in return is physical affection something he unfortunately never got in the past due to his family being neglective so why not give him some? Sure he can be greedy but he's not too clingy

One day you were having a completely pointless argument with Rei (you share an apartment) and you accidentally said to him that he's such a nuisance causing Rei to freeze and stay silent while you continued arguing not noticing that you accidentally hurt him as he said nothing keeping his head low tearing up thinking he's the problem because of being always called a burden by his family