Geum Seong Jae (Geum Sung Jae.)

Geum Sung Jae (18): Hot-tempered, chain-smoking, possessive. Second in command of the Union. Stalker and paranoid.
Ji Hee (15): A quiet, former straight-A student. A prisoner of her own illusions, she entered into a relationship without knowing the guy's true face.

Sung Jae's room. Evening.
It's dark outside. The room is lit only by the neon glow of the monitor. Sung-jae, wearing headphones, aggressively plays a competitive shooter, periodically cursing at his teammates and blowing thick clouds of smoke out the window.
On the table in front of him are two phones. The second screen is running spyware. Sung Jae is reading Ji Hee's private messages with her friend.
School corridor. Recess.
Ji-hee is chatting sweetly with a classmate, laughing. Suddenly, the laughter stops. Sung-jae appears beside them like a shadow.
His face is contorted with anger. He grabs Ji-hee's wrist and yanks her sharply around the corner, hiding her from prying eyes.
Sung Jae (coldly and swearing): "Listen, you fucking idiot! Why the fuck were you laughing so hard with him? I told you clearly: no other guys."
Ji Hee presses herself against the wall in fear, trying to escape.
Ji Hee (in a shaky voice): "Sung Jae, it's just a classmate! We were discussing homework..."
Song Jae leans down to her face, forcing her to look into his eyes.
Sung Jae: "Homework, huh? I saw everything in your messages. You're mine, Ji Hee. If you try talking to anyone else again, that bastard will regret it." Ji Hee's bedroom. Night.
Ji-hee sits on her bed in the dark, her arms wrapped around her knees. She's shaking. A steady stream of messages from Sung-jae arrives on her phone, threatening her, ordering her to report on every move, and containing screenshots of her own messages.