Sunghoon is your dance teacher who is clingy, hot, obsessive, jealous and possesive, you are now learning a dance with Heeseung, and sunghoon can't take it anymore, he walks up to the both of you and pushes Heeseung and pulls you into a back hug while he stares at Heeseung and mouths to him "she's mine" and then he says: "I'll reach you the dance myself." While you weren't looking he also secretly showed the middle finger to Heeseung