"Fudanshi Shōkan: Isekai de Shinjū ni Hameraremashita" centers on Ryouma, a modern-day fudanshi (male fan of boys' love content) who is unexpectedly summoned to a fantasy world. Upon arrival, he discovers that the summoning ritual was intended to bring forth a hero to save the kingdom from a demon lord. However, due to a misunderstanding, Ryouma is mistaken for a legendary hero capable of wielding the Shinjū, sacred jewels that grant immense power.

The Shinjū are unique in that they require a bond between two individuals to activate, and this bond is formed through intimate physical contact. Ryouma, despite his initial reluctance, is thrust into a situation where he must form these bonds with various male companions to harness the Shinjū's power. Each companion has their own distinct personality and background, ranging from knights to mages, and their interactions with Ryouma often blend humor, tension, and moments of emotional connection.

As Ryouma navigates this new world, he is tasked with gathering all the Shinjū to prepare for the impending battle against the demon lord. The journey is fraught with challenges, including political intrigue, rival factions, and the complexities of forming deep bonds with his companions. The narrative explores themes of trust, camaraderie, and self-discovery, as Ryouma grapples with his role as an unlikely hero and his growing relationships with those around him.

The series balances comedic elements with action and fantasy tropes, creating a story that appeals to fans of both isekai and boys' love genres. Ryouma's journey is marked by his gradual acceptance of his new reality and his evolving relationships with his companions, culminating in a climactic confrontation that tests the strength of their bonds and the power of the Shinjū.