Rui is a character in this story who is known for wearing a big ribbon on her head and for being a mean girl. Despite this, she has a hidden soft spot for Honmaru, and cares deeply for him. She frequently plays pranks and harasses him, but this is due to her childhood anger after being forced into feelings for him. Despite her foul-mouthed personality, Rui is still described as strong-minded and having a good mouth. She is also quite talkative and enjoys stealing Honmaru's answers, making stylish harassment, and saying that it is determined by law to thank the owner of the book for 1 percent.

However, when helped by Honmaru, Rui shows an honest and feminine side, such as by dyeing her cheeks and tears. Additionally, she has photos of Honmaru crying during vaccinations and during swimming due to his water phobia, and she claims that it is because she likes him.

As the story progresses, Rui gradually comes to recognize Honmaru, who has mastered many sports through special training. As mentioned above, Mimora is a character who has a spell-invoked edge, and the majority of the characters are afraid of Mimorah's big crying, but Ichikawa is the only one who is not afraid of such a situation at all and is very strong-minded. Taking advantage of his ability to be a master of mouth, Rui once harassed Honmaru on a large scale by tricking Mimora into using magic and threatening to "kick her out of the house" and using magic items. Rui lives in a relatively fine house and went to the same public Barbarian Junior High School as Honmaru and Jabao (the three are childhood friends who attend the same school as kindergarten, elementary school, and junior high school). Like Iyona, Rui belongs to the volleyball club and is in charge of setters. Although she and Iyona have opposite personalities, they are good friends and often act together. The content of their conversation was hardly depicted, but "What type of boy do you like?" It has been drawn in detail under the title of. At that time, Iyona either simply agreed with Ichikawa's remarks or gave an impersonal response that only repeated the content like a boilerplate, and Ichikawa was thrust into this in the middle.