Ryuzo Takehara practices as the sole physician on Sentan Island, specializing in geriatrics and tending to its aging population. His clinic languishes in disarray, with relatives routinely managing chores like laundry and meals to compensate for his neglect of domestic responsibilities. He navigates a tense marriage with his wife, Fusa, strained by his relentless work ethic and prolonged absences, yet their mutual devotion to their son, Akiyuki, anchors their fractured bond.

Once entangled in military research, Ryuzo developed humanform weaponry for the Northern Government—a chapter he vehemently regrets. He clings to ututu seeds, remnants of his clandestine experiments, unable to discard these artifacts despite renouncing his former path. This expertise surfaces when Akiyuki reappears fused with a Hiruko, prompting Ryuzo to urgently probe his son’s awareness of the parasitic entity’s motives.

After a terrorist strike destabilizes the island, Ryuzo employs life support systems to sustain Nazuna, the bomber who implanted the Hiruko in Akiyuki. His intervention stems from professional obligation and private remorse over his wartime contributions, blending medical duty with a need to atone. These choices reveal a nexus of guilt, intellectual rigor, and protective instincts toward both family and victims ensnared in the crisis.

During Akiyuki’s fleeting visit home, Ryuzo confronts him about the Hiruko’s agenda, exposing his unrelenting struggle to balance past sins against his present role as healer. Their exchange lays bare his unresolved anguish and determination to decipher the forces altering his son’s existence. Ryuzo’s legacy remains irrevocably tied to wartime consequences, positioning him as a linchpin between Sentan’s fragile peace and the geopolitical strife encroaching upon its shores.