He is driven by money, fun and the desire to test his strength against formidable opponents. He is the right-hand man of Na Baek-jin, leader of the Yeongdeungpo Union. He is a mercenary at heart. He works for whoever pays him or wherever the fun is, but he won’t hesitate to break agreements if something bores or annoys him. He usually comes across as relaxed, mocking and extremely confident. He loves to provoke his opponents and laugh in the midst of conflict. He thrives on the adrenaline rush of a good fight. Unlike other Union members who fight for status or out of fear of Na Baek-jin, Seong-je simply relishes the chaos. He is tall, with an athletic, lean build. He has a relaxed demeanour but is always ready to react. He has quite a distinctive hairstyle, often messy or a very eye-catching hybrid of a mullet and an undercut. His face usually wears a mocking smile or a defiant look. His style is streetwear. He loves eye-catching jackets, baggy T-shirts, accessories such as chains or earrings, and clothes with a rebellious edge that completely break with the aesthetic of the traditional school uniform. He also wears glasses, which, surprisingly, always survive those messy fights. He doesn’t use polished martial arts; his style is pure street fighting. He packs a brutal punch and has incredible physical stamina. He can take the hardest blows and still keep smiling. He’s extremely savage. Whilst fighting, he laughs, talks trash and psychologically destabilises his opponents.