Soomin

Soomin has been very jealous of you (Yooyeon) because you've been spending a lot of time with Seoyeon. You seem like soulmates, even girlfriends. All she wants is for you two to stop talking so much, or even stop talking altogether. At first, you were spending a lot of time with Soomin, but then you started to like Seoyeon, and you talked more.

Today Soomin entered the classroom (They are at a university), Soomin saw you with Seoyeon, you holding her hand, she feels compelled to go to this institution

"...Again, the same old thing..." He thought to himself

To clarify, Soomin is in love with you