Mirei Kudou is a supporting character in the story, serving as the student council president at Senkō Private High School. She is a teenage girl with fair skin and straight shoulder-length dark blue hair, which she typically ties up into a bun at the back of her head. Her role in the narrative begins when she visits the Literature Club to reprimand them for being noisy, and during that encounter she inadvertently reveals that she has also developed a supernatural ability. Her superpower allows her to steal another person's special ability and use it for herself, but this theft only works when the original wielder has already activated their power. This limitation means she cannot simply take abilities at will; she must wait for the target to use theirs first.

Mirei's personality is marked by a strong sense of duty and a serious demeanor, fitting her position as student council president. She is ambitious and competitive, often striving to be the best and seeking recognition for her efforts. Beneath her composed exterior, she is not immune to misunderstandings. A key event occurs when Jurai Andou writes her a letter intended to name her ability Grateful Robber, but he misuses a kanji character, causing Mirei to read it as Grateful Lover. She then interprets the letter as a love confession and briefly believes she is Jurai's girlfriend, leading to an awkward and comedic situation. When the misunderstanding is clarified, she is hurt but later accepts the intended name and apologizes, ultimately becoming friends with Jurai and the Literature Club. This incident highlights her earnestness and her capacity for emotional vulnerability.

Her motivations are initially tied to her role as student council president and her desire to understand the supernatural powers that have become common. She seeks to assert herself among the superpowered individuals, but she also yearns for connection and belonging. After the misunderstanding is resolved, she integrates more closely with the Literature Club, despite not being a formal member. Her relationships with the club members are characterized by these initial tensions and a gradual development into mutual respect and friendship. She shares a particular dynamic with Jurai, whom she initially misreads romantically but later regards as a friend.

Over the course of the story, Mirei experiences development in her understanding of others and her own place in the supernatural world. She is not a main protagonist, but her presence influences the group's dynamics. In later arcs, she becomes a target of manipulation by an antagonist named Genre Yusano, who implants an additional personality inside her to control her body. Under this possession, she attacks the Literature Club and uses her ability to steal the powers of the female members. However, she is defeated through Jurai's strategy and later freed from the control. This event tests her resilience and her bond with the club.

Her notable ability, which she refers to as Grateful Robber after Jurai's naming, is a power-stealing skill that can only activate when the original wielder has already triggered their ability. This power makes her a potentially dangerous opponent, but its conditional nature also limits her effectiveness unless she engages in combat where others are actively using their powers. Mirei's character adds depth to the series by exploring themes of identity, trust, and the challenges of navigating everyday life with extraordinary abilities.