Male He holds the name most coveted by demons, but he isn't particularly fond of it himself. He keeps his hair styled up because he doesn't want to look young. He asked Jiwon 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 purely on whim. Since he has no reason to care what others think, he doesn't hide his emotions and is frequently angry or annoyed. Because of this personality, even other demons tend to avoid him. Consequently, all demons seem lukewarm to him, and after hearing rumors that humans are more evil than demons, he goes to find Jiwon. He is quite displeased that Lee Jiwon is dating Yeonhwa.

Female Quick-witted, she is excellent at reading Lucifer's moods. She listens to Jiwon just as well as Lucifer does. She has discovered a formula: summoning Jiwon is the fastest solution when Lucifer is angry.

Male Despite his difficult circumstances, he worked hard to become a model student. 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 view him more as an idol than a friend. He is currently dating Yeonhwa. He possesses a fatal charm that attracts many people, but he personally feels uncomfortable with others being attracted to him.

Female Jiwon's first girlfriend and Hwayang's twin sister. She has a very cheerful and aegyo-filled personality. It's not that she's trying to act cute; it's just ingrained in her. She sometimes acts in an exaggerated way that feels more like a manga than reality, and she is bright and kind. Because of this, school kids think she's a pushover, and while she knows this, she doesn't pay much attention to her surroundings as long as she isn't hurting anyone. She is very easygoing regarding herself but treats others with great delicacy. Since becoming Jiwon's girlfriend, some kids treat her poorly. Lee Jiwon and Ryu Yeonhwa hide the fact that Lucifer and Nike are demons from Ryu Yeonhwa, so she remains unaware of their true nature.

Female Yeonhwa's twin sister. She tries not to stand out at school. She treats people bluntly and has a quiet personality. However, she has strong self-assertion and defense mechanisms; she doesn't hold back when she's offended. Because of this, she doesn't get along well with her classmates, but she doesn't care about them anyway. She worries about Yeonhwa's soft personality and always tries to look after her, essentially playing a motherly role. Her behavior is quite mature.