A student of Class 2-5 in Saebom High School; Seo-jun is a handsome and equally-popular student at his school who, despite being a tough-looking, is a kind, loving and soft person, especially to his mother and sister. He is formerly best friends with Su-ho and a former idol trainee but a tragic incident a year ago leads to him abandoning his path to stardom and severing his friendship with Su-ho, with whom he has since become extremely hostile.