"Hanimero" centers on Haine Otomiya, a high school girl who harbors a deep admiration for the handsome and popular student council president, Shizumasa Tachibana. However, her feelings are complicated by her belief that she is unattractive and unworthy of his attention. After a chance encounter with a mysterious woman, Haine is transformed into a beautiful, confident version of herself, allowing her to approach Tachibana more directly. This transformation, however, comes with a catch: she must maintain her new appearance by adhering to specific rules, including avoiding physical contact with Tachibana.

As Haine navigates her dual identity, she becomes entangled in the lives of Tachibana and his close friend, Rei Kashino, who harbors his own secrets and struggles. Rei, initially aloof and enigmatic, begins to develop feelings for Haine, creating a love triangle that adds tension to the narrative. The story explores themes of self-esteem, identity, and the complexities of relationships, as Haine grapples with the consequences of her transformation and the authenticity of her connections with others.

The series delves into the dynamics of the student council, where Tachibana and Rei play central roles, and introduces additional characters who contribute to the unfolding drama. Haine's journey is marked by moments of humor, romance, and introspection, as she learns to reconcile her inner self with her outward appearance. The plot progresses through a series of misunderstandings, emotional revelations, and personal growth, culminating in a resolution that addresses the central conflicts and relationships. "Hanimero" balances lighthearted moments with deeper emotional undertones, offering a narrative that appeals to fans of romantic comedies with a touch of fantasy.