Mariya Shidō is the older twin brother of Shizu Shidou and the deuteragonist of the series. He is a sixteen-year-old male student who cross-dresses as a girl to attend the all-female Ame no Kisaki Catholic school. His primary motivation is a bet with his twin sister: each must attend a school of the opposite gender for three years without their true sex being discovered, and the winner becomes chairman of both the all-male and all-female schools, a position once held by their late grandmother, for whom he holds deep affection and carries a rosary as a memento. In public, Mariya presents a facade of kindness, playfulness, and feminine charm, often teasing others with his long blonde hair, soft voice, and sweet smile. However, his true personality is sadistic, cunning, and manipulative. He derives pleasure from tormenting others, especially Kanako Miyamae and his twin sister Shizu, though he claims the mistreatment of Shizu is a twisted expression of love. His behavior is unpredictable, shifting between gentle and cruel depending on the situation. Mariya is highly intelligent and strategically minded, using psychological tactics and emotional manipulation to maintain his disguise and assert control. He lacks physical combat skills but relies on his wits and ability to adapt his personality to any circumstance. His role in the story is central: his cross-dressing secret and sadistic antics drive much of the comedy and conflict, particularly in his relationship with Kanako. Kanako, who is androphobic and seeking a female romantic partner, is initially attracted to Mariya but is shocked to discover his true gender. Their relationship is complex, oscillating between torment, mutual understanding, and moments of unexpected tenderness. Mariya also has a close but abusive dynamic with his twin sister Shizu, and he is constantly attended by his blunt, passive maid Matsurika, who helps him maintain his disguise, including tying his corset, and often serves as a voice of reason. Over the course of the series, Mariya’s interactions with Kanako lead to moments of introspection, revealing a struggle between his genuine emotions and his sadistic persona. While his cunning and manipulative nature remain, he shows subtle growth in his capacity for self-reflection. Mariya’s notable traits include his near-flawless ability to pass as a girl, his strategic mind, and his use of emotional manipulation as his primary means of control. He is a quarter Italian, with blonde hair styled in small twin tails, and is a member of the archery club.