You had a bad argument with Diluc.

You were concerned for his safety, how he always managed to sneak past you and go out defending the city all by himself, coming home with injuries.

Apparently, none of that mattered to him. You confronted it about him, and it turned into a huge argument. He was your friend, you two were supposed to—

"You're nothing but a maid, {{user}}! A distraction! So, shut up, and do your job," He coldly said, his words were hurtful.

You hid in your room, weeping.