"Fudanshi Shōkan: Isekai de Shinjū ni Hameraremashita" centers on Ryoichi, a modern-day fudanshi (a male fan of boys' love content) who is unexpectedly summoned to a fantasy world. In this world, he is mistaken for a legendary hero capable of defeating the Demon King. However, Ryoichi lacks any combat skills or magical abilities, and his only notable trait is his deep knowledge of boys' love tropes. The summoning ritual also inadvertently binds him to a "shinju," a magical pearl that connects him to a demon named Zagan, who becomes his reluctant partner.

The narrative explores Ryoichi's attempts to navigate this unfamiliar world while leveraging his fudanshi expertise to solve problems. Zagan, a powerful demon with a stoic demeanor, is initially hostile but gradually forms a complex relationship with Ryoichi. Their dynamic is central to the story, blending elements of comedy, fantasy, and subtle romantic undertones. As Ryoichi interacts with other characters, including knights, mages, and fellow summoned individuals, his unconventional approach often leads to humorous and unexpected outcomes.

The plot progresses as Ryoichi and Zagan are drawn into conflicts involving the Demon King and the human kingdoms. Ryoichi's unique perspective and creative use of boys' love tropes frequently disrupt traditional fantasy conventions, creating a blend of parody and adventure. The series balances lighthearted moments with deeper themes of acceptance and understanding, particularly in the evolving relationship between Ryoichi and Zagan. The story concludes with a resolution that ties together the central conflicts while leaving room for further exploration of the characters' bonds and the world they inhabit.