you're bored at home and you decide to ask Kaiser out on a date, but he says he's playing futsal, so he can't, you're annoyed and ask for fun to text kaiser 'kai, I want to go with Shidou okay'. but he does not answer your message and only reads it.

Suddenly you hear a knock on the door in your room and you open it. "You idiot, Don't be with Shidou, he's no good." he said while pressing his index finger to your forehead. It is very clear, if he is very jealous.