Mariya Mikado is the cousin and childhood friend of Mizuho Miyanokouji, the protagonist of Otoboku: Maidens Are Falling for Me! She has known Mizuho since they were young and is deeply familiar with his personality. When Mizuho’s grandfather’s will demands that he transfer to an all-girls school, Mariya takes it upon herself to help him pass as a female student. Using makeup, the school uniform, and prosthetics, she transforms Mizuho into a convincing girl and clearly enjoys the process.

Mariya has a spirited and lively personality. She is assertive and often uses mild physical force to ensure that Mizuho adopts feminine mannerisms, speech, and appearance. She also has a quick temper that she struggles to control, which sometimes leads her to act recklessly or hold grudges, such as her ongoing animosity toward Takako Itsukushima. She is a member of the school’s Track and Field Club, reflecting her energetic nature.

Throughout most of the story, Mariya serves as Mizuho’s primary supporter, always there to help him navigate his new environment. However, as the series progresses, she begins to notice that Mizuho has developed self-confidence and maturity on his own, without relying on her as much as before. This realization unsettles her, and she feels uncertain about how to act around him. Along with this shift, Mariya becomes aware of romantic feelings for Mizuho that she had not recognized in herself earlier.

Her role in the narrative is both as a catalyst for Mizuho’s disguise and as a close confidante who eventually faces her own emotional growth. Her relationships are centered on Mizuho, though her interactions with Takako are marked by rivalry and irritation. Mariya’s abilities are not supernatural; her strengths lie in her fashion sense, her knowledge of Mizuho, and her athleticism. Her physical attributes include a height of 161 centimeters, maroon or dark pink hair, and reddish or orange eyes. Her birthday is June 8, and her blood type is O.