"Biorg Trinity" is a science fiction manga series set in a surreal and dystopian world where humanity is plagued by a mysterious phenomenon known as "Bio-Organisms" or "Biorgs." These Biorgs are parasitic entities that fuse with humans, granting them extraordinary abilities but often at the cost of their humanity. The story centers on Fukuya Igarashi, an ordinary high school student whose life takes a drastic turn when he becomes entangled in the conflict surrounding Biorgs.

Fukuya's classmate, Inori Akizuki, is revealed to be a Biorg host, and her presence triggers a series of events that draw Fukuya into a hidden war. Inori is pursued by powerful organizations and individuals seeking to exploit her unique abilities, as she is believed to hold the key to unlocking the true potential of Biorgs. Fukuya, despite his initial reluctance, becomes determined to protect Inori, even as he begins to uncover unsettling truths about his own existence and connection to the Biorg phenomenon.

As the narrative progresses, Fukuya and Inori encounter a diverse cast of characters, each with their own motivations and ties to the Biorg conflict. These include enigmatic figures like the Biorg hunter Kuroki, who operates with her own agenda, and the mysterious organization known as the "Trinity," which seeks to control the evolution of Biorgs for their own purposes. The story delves into themes of identity, transformation, and the blurred line between human and monster, as characters grapple with the consequences of their choices and the nature of their existence.

The plot is driven by a mix of action, mystery, and psychological exploration, with the characters navigating a world where reality is often distorted and the boundaries of life and death are unclear. The Biorgs themselves are depicted as both a source of power and a curse, with their integration into human hosts leading to unpredictable and often tragic outcomes. The series builds toward a climactic confrontation that challenges the characters' understanding of their world and their place within it, culminating in a resolution that leaves lasting implications for the future of humanity and the Biorgs.