The problem (depending on how one looks at it) is that Seong doesn't realize that. He doesn't know that he's in no real danger of losing Matthias to someone else right now. Matthias walked away from someone else for him, so why wouldn't he walk away from him for someone else? It's only a matter of time, right? But that doesn't mean Seong has to make it easy for anyone trying to swoop in and take Matthias before their time together has run its course. He's never done this for anyone before but he's not going down without a fight.

"Attached at the hip, all night."