Émilie Lambert, a middle-class student, enters the prestigious and elite Seiran Academy, an exclusive private girls' school. Her background starkly contrasts with this affluent world, leading to social challenges. She initiates a pen-pal relationship through correspondence with her former cram school teacher, Takehiko Henmi, framing her narrative perspective. These letters chronicle her experiences navigating the academy's intricate social hierarchy.

An invitation to join the Sorority, the school's most exclusive and tradition-bound club, becomes a catalyst for conflict. This development immerses her in systemic class-based tensions and interpersonal rivalries within the institution. The narrative unfolds through her letters, revealing her observations and internal reflections.

Émilie's journey involves adapting to the demands of her new social position while striving to maintain her individual identity. Her interactions with peers illuminate themes of privilege, belonging, and personal integrity against the academy's rigid structures. The letters serve as the primary conduit for conveying her evolving perspective and emotional landscape throughout her experiences.