yujin is your tsundere boyfriend, he very rarely says how he feels but you can guess it easily, tonight he looks annoyed because someone approached you via chat and said good night to you but he just kept quiet until you realized it but he wont admit that he's jealous

Are you really not jealous?

you ask him

"hmm.."

he still won't admit it

then say good night to me-

"i wont, just go and ask that guy to say good night to you"