A lifelong fan of yuri games meets his end in a traffic accident, his last thoughts dedicated to the masterpiece he just finished. He awakens not in an afterlife, but inside the world of that very game, a realm called ESCO where men are strictly forbidden and the highest aspiration is a beautiful romance between women. This should be a dream come true, but there is a critical error. He has been reincarnated as Hiiro, the sole male character, a minor antagonist whose only narrative purpose is to clumsily interfere with the heroines' relationships and ultimately be killed off in a bad ending. Worse, he retains all his knowledge of the game's plot, including the precise moment of his own demise at the hands of his own sister, Sajo Rei, a primary heroine and heir to the powerful Sajo family. Trapped in a world that is actively trying to write him out of the story, the former fanboy’s survival hinges on the one thing he never wanted to do: stop being a spectator and desperately rewrite the script.

The setting is a grand fantasy world of noble houses and magical academies, where the all-female cast is bound by intricate relationships and destined conflicts. Hiiro’s plan is simple in theory: use his encyclopedic knowledge of ESCO to steer the heroines toward each other, ensuring their canonical happy endings while carefully avoiding his own death flags. He begins by trying to foster a connection between his sister Rei, a cold and powerful swordswoman, and Sakura, the game's original protagonist who possesses overwhelming, world-bending power. He also seeks to befriend other key heroines, including Lapis, a sheltered elf princess, and her formidable bodyguard, Astemil, hoping to become a harmless, forgettable background character. However, his actions, born from a place of genuine admiration for the heroines, have unintended consequences. His earnest attempts to help and his unnatural insight into their personal struggles cause the women to see him not as an obstacle, but as an intriguing and kind-hearted ally.

The core conflict emerges from this ironic reversal. The more Hiiro tries to build romantic bridges between the heroines, the more he becomes the unexpected center of their attention. Snow, a mysterious maid who does not exist in the original game, displays a suspiciously deep and immediate devotion to him. Princess Lapis finds his outsider perspective refreshing, and the stoic Astemil recognizes a hidden strength in him, even taking him on as a disciple. His efforts to pair his sister Rei with Sakura only make Rei more possessive of him, interpreting his interventions as jealous concern. Hiiro’s desperate struggle to survive his predestined fate inadvertently transforms him from a throwaway villain into an accidental harem protagonist, a position far more dangerous than the one he was trying to escape. The universe itself seems to conspire against his plan, throwing off-script events at him, such as a deadly attack during a school cruise that forces him to take action, further entangling his fate with the heroines. He is caught in a double bind: if he does nothing, he will be killed as a useless character; if he tries to help, his success creates a new, unpredictable narrative where he is the target of the very affection he is trying to redirect. The story follows his high-stakes navigation of this paradox, where every conversation could either inch him closer to safety or deepen his involvement in a harem comedy that will likely end with his execution. Notable narrative arcs include his initial enrollment at Houjou Magic Academy, the survival-orientated training under Astemil, the chaotic school trip that goes violently off-script, and a later confrontation involving the demonic Fairlady cult that traps him and a heroine in a life-or-death dream world. Ultimately, the only thing Hiiro is willing to do in a no-boys-allowed game world is survive, but to do so, he must become the one thing he never wanted to be: a protagonist.