"Fudanshi Shōkan: Isekai de Shinjū ni Hameraremashita" centers on Ryouma, 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 divine beast kings. The narrative explores Ryouma's struggle to reconcile his identity and desires with the expectations placed upon him by this new world.

The four beast kings—Shin, the dragon king; Byakko, the white tiger king; Suzaku, the phoenix king; and Genbu, the tortoise king—each represent different elemental powers and personalities. They are bound by a prophecy that requires them to unite with the Sacred Bride to maintain balance in their realm. Ryouma, however, is initially resistant to this role, as it conflicts with his personal interests and understanding of relationships.

As the story progresses, Ryouma forms complex relationships with each of the beast kings, navigating themes of duty, identity, and consent. The series blends elements of fantasy, romance, and comedy, often juxtaposing Ryouma's modern sensibilities with the archaic traditions of the fantasy world. The narrative delves into the dynamics of power, trust, and mutual understanding, as Ryouma gradually comes to terms with his role and the feelings he develops for the beast kings.

The plot is driven by both external conflicts, such as threats to the kingdom, and internal struggles, particularly Ryouma's journey of self-acceptance and the beast kings' evolving perceptions of their roles and relationships. The series balances lighthearted moments with deeper emotional exploration, creating a multifaceted narrative that appeals to fans of both fantasy and romance genres.