Niki, once a socially ostracized high school student, endures relentless bullying and emotional abuse that erode his fragile psyche. His unrequited longing for Akemi and simmering jealousy toward Nagumo morph into bitter resentment, attracting demonic entities that manipulate him into opposing the Chōjin. They grant him power through a grotesque ritual: replacing his genitalia with a demonic phallus in exchange for heightened abilities, a transformation marked by visceral auditory and visual horror.

Emerging from this ordeal, Niki becomes a muscular, sadistic enforcer who wields his newfound strength to dominate others, perpetuating cycles of cruelty he once suffered. His descent into hedonism and sexual violence is punctuated by fleeting vulnerability, such as apologizing to a partner he harms mid-encounter—a moment sparked by her resemblance to Akemi, hinting at fractured remnants of humanity beneath his corruption.

His downfall peaks during a clash with Nagumo, now bonded to the Chōjin. Desperate to assert control, Niki forces Akemi into degrading acts to spare Nagumo, exposing his warped obsession intertwined with lingering affection. Nagumo, empowered by the Chōjin, ultimately destroys him. In death, Niki clutches an object tied to Akemi, a silent testament to his unmet yearning and moral unraveling.

Rooted in a past defined by alcoholic, abusive parents and peer exploitation, Niki’s arc frames societal alienation as a catalyst for supernatural manipulation. His tragic trajectory underscores the corrosion of empathy and the destructive allure of vengeance, positioning him as a cautionary figure consumed by power’s corrupting grip.