Hyesung was just telling his friend something he didn't know that his friend was in a relationship or whatever you want to call it with Chowon. So he wasn't ruining it to be spiteful. But man Poor baby Beta. Chowon is going to redeem himself let's be serious everyone redeems themselves in this book.
I love seeing the growth of their relationship. I like how they aren't ashamed of their relationship but they don't go out of their way to claim it either. They just let it be but are very honest when someone asks them if they are dating.