The setting is like that of a medieval period fantasy RPG. Like in an RPG, Komomo's sword disappears when she is not using it. Sometimes in the background is a small cactuar - a common enemy in RPGs. Some demons look and act like monsters, but many have an appearance and a personality like a human's.
In the story, in order for someone to raise their level, they have to take a level qualification exam. The exam costs money and since Komomo is poor, she can't afford to take it. However, level 0 heroes don't get paid much for their work, so Komomo can't earn the money to take the exam. In order to gain a fortune, she tries to kill the Maou (魔王?), or Demon Lord, who is at level 2000, but she is unable to due to the tremendous difference in their levels. Instead, the Maou falls in love with her and sacrifices everything to be with her. She agrees to let him travel with her, claiming it would be irresponsible for a hero to allow an ex-Maou to roam free.
The second volume is subtitled THE OTHER SIDE OF LYCANTHROPE and focuses on Kurenai, Carol, and a new character. This new character becomes cursed after seeing a mummified Lycanthrope hand. The curse causes her personality to become like a dog's personality at times. However, if the curse is not lifted by the next full moon, she will transform into a wolf permanently. Kurenai and Carol journey with her to find the Maou, believing that he might know how to lift it.
- Komomo Sakurai (小桃·サクライ Komomo Sakurai?) - a seventeen year old, poor, level zero hero. Her mother died when she was young, and ever since then, her goal has been to build a house with a red roof and a chimney. She is a Magic Holder or a human who has the magical powers of a demon. Magic Holders are distinguished from other humans by their pure white hair and skin, and are disliked by both humans and demons alike.
- Subaru (昴·ハーネスト Subaru Hānesuto?) - the twenty year old Maou. He is at level 2000, and at the start of the series, he is bored of being on top of the world. He falls in love with Komomo, the hero who always comes to try to defeat him, but can never do any damage due to their vast difference in level. He gives up being the Maou in order to protect her from subordinates that disapprove of his love for a human. His right hand is the Lycanthrope - the hand of the first Maou, which grafted onto the next Maou's arm. The hand desires to shed human blood, but by rejecting that desire, Subaru's body begins to reject the hand. In turn, the hand begins to painfully take over his body.
- Kurenai (紅·アカツキ Kurenai Akatsuki?) - a nineteen year old demon with a dark personality and a sour attitude. He is one of Subaru's closest subordinates and travels with Carol. He made medicine to slow the rejection of Subaru's Lycanthrope. While he appears tough on the outside, Kurenai is actually a caring person as shown when he protects Subaru from those who are trying to obtain the Lycanthrope for the next Maou. It is revealed in the omakes that he likes animals, especially dogs. His weapon of choice is a katana. Also, it is implied that he has a crush on Purino, but he constantly denies it and calls it an, "ireversable" relationship; however, he does care for her to a great extent.
- Carol Bluehouse (キャロル·ブルーハース Kyaroru Burūhāsu?) - a fifteen year old demon who loves housework. His specialty is shikigami. He is also one of Subaru's closest subordinates. Carol always has a polite way to describe a person. He travels with Kurenai. He likes to tease Kurenai about his feelings for Purino.
- Purino Howell (プリノ·ハーウェル Purino Hāweru?) - a seventeen year old demon who is a general (将軍 shōgun?) but also a klutz. She played violin when she was younger, but gave it up because she was worried that her family would become upset with her if she continued to be a poor violin player. She had a crush on Subaru, who she thought was the one who encouraged her when she was chosen to give a speech for her military designation ceremony. However, it turned out to really be Kurenai, who was acting as the Maou's body double. She only appears in volume two. It is revealed she comes from a rich family. Carol teases Kurenai, saying that they should keep it a secret otherwise Purino will have stalkers and Kurenai will have more rivals.
- Ume (梅 Ume?) - a magical dog whose mouth is a portal to another dimension. Subaru gives him to Komomo after she takes an affection to him. Ume spits out clothing for Komomo whenever she needs some.
At the end of volume 1, there is an omake portraying the characters in a different setting. It roughly follows the same storyline as the main storyline, but depicts it in a more comical and condensed manner.
CALLING (コーリング Kāringu?) was Fujiwara's debut work when she was fifteen. It appeared at end of the volume 2 tankōbon. The story begins with two beings of the underworld - Cruel and Karlo - dueling over who would become the ruler. However, Cruel is accidentally summoned to the human world because of a magic circle made by a human girl named Pearl. The summoning causes Cruel to become Pearl's servant and lose his ability to use magic properly, thus giving him no way to return. Pearl is a kind girl who goes above and beyond to help others, and she tries to help him find a way to go back home. Cruel is confused by this, but before he has a chance to understand her behavior, Karlo appears and challenges Cruel to finish their duel. Realizing Cruel cannot use magic, Karlo tries to kill Pearl as that would release Cruel from servitude. However, Cruel throws himself in the way, even though he cannot create a magical barrier to protect himself. Karlo is astonished but Cruel explains that he has come to care for humans.
STRAY DOLL (ストレイ·ドール Sutorei Dōru?) was a short story that came after CALLING in the volume 2 tankōbon. The story revolves around a young man named Fiz who is a Doll Master. A Doll Master is someone who can control dolls with his will; Fiz uses a marionette control bar to control his dolls. A stray doll is a doll that is controlling itself with no master. When a doll is being controlled or becomes a stray, it grows to a much larger size and changes its form. Fiz hunts down stray dolls with his companion Reiou (麗王?, lit. Lovely Sovereign) who is a doll. All the names of the Fiz's dolls named in the story end with ou (王?, king or ruler). The story covers Fiz and Reiou visiting a town to capture a dangerous stray doll.