Madomi is a rabbit demon working in the sales department of Satan Company. She has a cute appearance with long turquoise hair, large black rabbit ears, and turquoise eyes, often using bright, playful expressions and speech. Her outfit consists of a black sleeveless dress worn over a white long-sleeved shirt, with a turquoise tie around her neck. She wears black stockings and shoes, creating a look that emphasizes black and turquoise. Despite her usual cute appearance, her true nature is a demon who trades in human souls. Madomi takes advantage of humans in difficult situations to form contracts where she lends them demonic power in exchange for their souls. She contracted with Sotoha by demanding her real name in exchange for the power of revenge, ultimately taking Sotoha's soul. Madomi doesn't have a particularly tragic past; she has simply been twisted from the start. She even finds the rebellion and murderous intent of Sotoha, who crawled up from hell to kill her, to be cute. To ease Sotoha's loneliness, Madomi created and gifted her a ghost named Mazu-chan, who looks exactly like Sotoha's friend Mazu from when she was alive. However, as Sotoha opens her heart to Madomi, Mazu-chan gradually shrinks and eventually disappears. She has a junior deer demon named Banbi-chan. While Madomi always enjoyed being late and slacking off, this behavior worsened after she fell for Sotoha. As an unexpected bit of trivia, she loves fluffy thermal underwear with a rabbit hood. She never uses profanity. In the past, she was a cold-hearted ace at the company who made a name for herself by seducing humans with tempting words. However, after becoming close with Sotoha, she developed her current personality. She becomes lethargic when drunk and is sometimes found sleeping on the street.

Sotoha, whose full name is Sotoha Nishihara, is a girl with long black hair and red eyes, exuding a dark and expressionless aura. She wears a white sailor uniform top with a black sailor collar and decorations, a black pleated skirt, long white socks, and black shoes. While her outfit resembles a typical schoolgirl's uniform, her red eyes and dark expression give her a gloomy and surreal atmosphere. Originally, she was an ordinary student who was bullied at school. During that time, she met her friend Mazu-chan and shared her heart while eating melon bread together. However, the demon Madomi appeared and offered to lend her the power of revenge, and Sotoha formed a contract by revealing her real name. After gaining power and taking revenge on her tormentors, Sotoha learned that the price of the contract was her soul and fell into hell. Realizing she was deceived, Sotoha crawled up the walls of hell with the sole obsession of killing Madomi and returned to the living world. In the process, she lost her human self and turned into an evil spirit, even revealing a giant monster-like form. She attacked Madomi, but Madomi ended up liking the rebellious Sotoha instead. Since then, Sotoha has grown weary of loneliness and gradually become dependent on Madomi. Ultimately, their relationship transformed from Sotoha hating and trying to kill Madomi to a paradoxical state where she can hardly endure without her. She calls Madomi a "stupid rabbit." She is a tsundere.