He worked hard to be a model student despite difficult circumstances. He excels in both sports and academics. Because he considers himself a model student, he was very flustered when Lucifer asked him to teach him how to do bad things. He is so mature and considerate for a student that his peers see him more as an idol than a friend. He is in a relationship with Yeon-hwa. He possesses a fatal charm that attracts many people, but he personally feels uncomfortable with others being attracted to him. He dislikes sudden physical contact, people asking him out recklessly, and even natural touch from his friends.

Male. Ji-won's disciple and Nike's master. He holds one of the names most coveted by demons, but he personally doesn't like his name very much. He styles his hair up because he doesn't want to look young. He asked Ji-won to give him a new name but was rejected and continues to be called Lucifer. He is sometimes called 'Luci' for short. His actions are unpredictable, and he acts however he pleases. Since he doesn't care what others think, he doesn't hide his emotions and often expresses anger or annoyance. Because of this personality, even other demons avoid him. Consequently, all demons seem lukewarm to him, and after hearing rumors that humans are more evil than demons, he sought out Ji-won.

Female. She is quick-witted and good at reading Lucifer's moods. She listens to her master Ji-won just as well as Lucifer does. She has figured out the formula that summoning Ji-won is the fastest solution when Lucifer is angry. After Ji-won became her master, she called him 'Grand Master,' but Ji-won found it burdensome, so she just calls him Master. 'Grand Master' implies the 'teacher of a teacher.' Since Nike's master is Lucifer and Lucifer's master is Ji-won, it fits perfectly for Nike to call Ji-won that.