"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 identified as the "Sacred Bride," a figure destined to bear the children of the Four Sacred Beasts—dragon, phoenix, tiger, and turtle—to restore balance and harmony. Despite his initial shock and reluctance, Ryoichi is drawn into the responsibilities and challenges of his new role.

The narrative explores Ryoichi's interactions with the Four Sacred Beasts, each of whom possesses distinct personalities and powers. The dragon, Ryuuga, is proud and protective; the phoenix, Suzaku, is flamboyant and passionate; the tiger, Byakko, is stoic and disciplined; and the turtle, Genbu, is gentle and wise. As Ryoichi navigates his relationships with these beings, he must also confront external threats to the world, including dark forces seeking to exploit the Sacred Beasts' powers for their own gain.

The story balances elements of fantasy, romance, and comedy, with Ryoichi's modern sensibilities and fudanshi tendencies often clashing humorously with the traditional and mystical nature of the world he inhabits. His journey involves not only fulfilling his role as the Sacred Bride but also understanding the deeper connections between the Sacred Beasts and the world's fate. The series delves into themes of duty, acceptance, and the complexities of relationships, all set against the backdrop of a richly imagined fantasy realm.