Mizuho Miyanokouji, a young man raised in an all-female environment, is sent to the prestigious all-girls school Otoboku Academy by his grandfather. The school, known for its tradition of admitting only female students, has made an exception for Mizuho due to his grandfather's influence. To avoid disrupting the school's norms, Mizuho is required to disguise himself as a girl and adopt the identity of his late sister. This decision sets the stage for a series of comedic and dramatic situations as Mizuho navigates life at the academy while keeping his true gender a secret.

At Otoboku Academy, Mizuho becomes the target of affection for several female students, each with distinct personalities and backgrounds. Among them is Takako Itsukushima, the student council president, who is initially suspicious of Mizuho but gradually develops feelings for him. Kanna Iwashimizu, a childhood friend of Mizuho, also attends the academy and harbors deep feelings for him, though she struggles to express them. Other notable characters include Mariya Mikado, a cheerful and outgoing classmate, and Shion Sumeragi, a reserved and mysterious girl with a strong sense of duty.

The narrative explores themes of identity, love, and the complexities of relationships as Mizuho balances his dual identity and the growing affections of his peers. The series blends elements of romantic comedy with moments of introspection, as Mizuho grapples with the ethical implications of his deception and the emotional consequences of his interactions. The story progresses through a series of episodic encounters, each highlighting the dynamics between Mizuho and the various girls, while gradually revealing more about their individual struggles and aspirations.

As the series unfolds, Mizuho's secret becomes increasingly difficult to maintain, leading to moments of tension and revelation. The relationships between the characters evolve, with some discovering Mizuho's true identity and others remaining unaware. The narrative culminates in a resolution that addresses the central conflicts, though it leaves room for interpretation regarding the future of Mizuho's relationships and his place within the academy. The series maintains a lighthearted tone while occasionally delving into more serious themes, creating a balance between humor and emotional depth.