Mirei Kudō is the student council president at the high school attended by the members of the Literature Club. She awakens a supernatural ability of her own, separate from the club, and initially approaches them with hostility after being tipped off about their powers. Her ability, later named Grateful Robber by Jurai Andō, allows her to steal and temporarily use the supernatural power of any person whose activation she directly witnesses. This ability makes her a potentially dangerous opponent, though its effectiveness depends on what power she can copy.

Mirei is a capable and diligent student council president who takes her duties seriously, often reprimanding the Literature Club for their noise, especially because of Jurai's loud chunibyō antics. Despite her responsible position and strong academic record, she has a tendency to be impulsive and prone to misunderstandings. This is most famously demonstrated when she misreads the kanji in Jurai's letter naming her ability—interpreting Grateful Robber as Grateful Lover—and briefly believes she has received a love confession. She becomes infatuated with Jurai during this period, showering him with over-the-top affection and declaring herself his girlfriend, much to his confusion and the irritation of the other girls. When Jurai gently clarifies the mistake, she is initially heartbroken but later accepts the situation with grace, apologizing and acknowledging the name he gave her power.

After the misunderstanding is resolved, Mirei becomes an occasional ally and acquaintance of the Literature Club. She continues to interact with them in her capacity as student council president, and she develops a lingering, one-sided rivalry with Jurai, finding his antics both frustrating and intriguing. She often represents a more serious, rule-abiding perspective on their supernatural abilities, serving as a contrast to the club's casual and playful approach. In later story arcs, she becomes involved in the larger conflict known as the Fairy War, where her ability is exploited by others for its power-stealing potential.

Personality-wise, Mirei is bossy, proud, and easily irritated, but also earnest and capable of genuine vulnerability. Her motivations center on maintaining order and proving herself, both as a student council leader and as an ability user. She struggles with the feeling of being left out of the club's close-knit dynamic, which partly drives her initial antagonism and later her desire for recognition. Over time, she learns to accept her place outside the club while still maintaining a cordial relationship with its members. Her development involves moving from a figure of comic misunderstanding to a more nuanced character who finds her own role in the supernatural world without being a core member of the Literature Club.