When active in the human world, he goes by the name Yoo Seung-chan. Both the name and identity are fake; his true identity is the demon Lucifer. His name is derived from the fallen angel Lucifer of Christian culture. He is dating Shurin, and they often bicker. Male.

In the demon realm, she has purple skin and horns. As mentioned later, this makes her incredibly popular. Even in the human world, she is very beautiful and popular in her human form. She is dating Lucifer and serves as a department head in the demon realm. Her personality is not great. Female.

He likes Shurin even though he knows she is dating Lucifer. He confesses to Shurin often but gets rejected every day. He is also a demon and has a terrible personality. He does not get along with Lucifer. He is Shurin's old childhood friend, and their parents are close. He comes from a wealthy family. Male.

Shurin's father. He seems to have more power than King Yeomra and is one of the main characters. It was said he was in danger of dying because of Lucifer, but he actually faked it to kill Lucifer. He doesn't like Lucifer much and is a demon. Male.

The King of Hell. He has a bad personality and hates Lucifer. Male.

He has a good personality and is human. He is Lucifer's (Yoo Seung-chan's) only friend in the human world. He doesn't know Shurin is trying to kill him. He doesn't even know Shurin exists. He is unaware that Lucifer is a demon. Male.

A demon who hates Shurin intensely. He is trying to kill her. He has a younger brother, Uraktos, who works under Shurin.

Shurin's only human friend, whom she met while on vacation in the human world. She has a bright and cheerful personality. She doesn't know Shurin is a demon. She talks to Shurin a lot, but Shurin finds her annoying. Female.