
Well yeah cuz as soon as your friend gets with someone you don't approve of or even someone else you do approve of, all good friends get jealous of the other person because you want to hang out with your friend and now you can't. The first time I ever got jealous wasn't because of a boy I liked or anything, it was because my best friend got a boyfriend I hated him for a long time because I was jealous he spent more time with her now.

I can understand that, but this was just a date and if you really cared about and loved your friend you wouldn't want to destroy their date, relationship etc.. jealousy is completely fine, but following her and starting shit is in my opinion, very excessive.. therefore, I guessed that maybe he is in love with her
Is Jun perhaps in love with Kohaku? Otherwise, I wouldn't understand why he wants to destroy her date...