For Ren Kisaragi, once an ordinary high school boy, that day became the most memorable and worst day of his life—the day his existence collapsed and was rewritten.

Whether it was a sudden physiological mutation of unknown cause or an inescapable bloodline curse, the person in the mirror was no longer his familiar self, but a beautiful, unknown girl. Even with the pinnacle of medical science and research, the ruthless verdict was handed down: "There is no way to return to your original form."

Desperate, Ren was presented with a single choice: erase his legal identity and live an entirely different life as Renge Kisaragi. For his own safety and to isolate him from the public eye, he was sent to St. Ariana Academy, a prestigious, all-girls boarding school—a sanctuary cut off from the mundane world where high-born young ladies gather.

Clinging to his memories and soul as a man, Ren is forced into life at the girls' dormitory, his body wrapped in the soft fabric of a school skirt. Between his roommate Himari, who smiles innocently at his side, and the student council president Hyoka, who watches him with a sharp gaze, his heart screams in protest as a man at their overwhelming proximity. Yet, his body begins to adapt to these "girly" days with cold efficiency.