You and Katsuki were secretly dating. No one knew about your relationship. Not even his parents. BUT, his mother knew that you liked him so she entered her sons room

Katsuki, do me a favor. Be sweet to Akari. She kind of has a crush on you. Mitsuki says

Really? I had no idea looks at his mom trying to hold back his laughter

Of course you didn't, boys never do. she replied and walked of his room

Katsuki started to laugh