Hisoka Kazaya serves as bodyguard to Orihime Kazaya, heir to a large conglomerate. To protect her covertly, he cross-dresses as a female student at St. Ceral Girl's Academy. Orihime discovers his secret during an attempted joint bath exposure. Mirei Masaki later uncovers his true gender after observing him apply prosthetic breasts while changing.

Hisoka achieves the academy's highest academic grades, earning him designation as one of the school's "Twinkle Stars"; Orihime and Mirei rank second and third.

Hisoka's cross-dressing is reported to Orihime's father, revealing Hisoka is actually Orihime's cousin and the conglomerate's true successor, having been entrusted to adoptive parents after a past family tragedy. Orihime acknowledges romantic feelings for Hisoka and confesses her love.

Following the kidnapping of both Hisoka and Orihime, Hisoka incapacitates their captors while restrained. He formally assumes the role of successor and announces his engagement to Orihime.

Hisoka intervenes again when Mirei faces a forced marriage after her father's bankruptcy, an investor demanding her hand in exchange for financial aid. Hisoka infiltrates Mirei's confinement hotel, defeats her guards, and rescues her. An alternative narrative outcome depicts Hisoka marrying Mirei instead, with her supporting his role as company successor.