The series follows Nanno, an enigmatic, immortal entity who materializes in various high schools and institutions. She serves as an agent of karma, manipulating human weaknesses—such as greed, vanity, lust, and jealousy—to expose the dark undercurrents of
modern society. Rather than acting as a traditional moral judge, Nanno acts as a catalyst, pushing morally compromised individuals past their breaking points until their inner wickedness consumes them.In each standalone episode, Nanno adopts the persona of a new student or faculty member, seamlessly embedding herself into toxic environments. Her targets are usually ordinary students, teachers, or administrators desperate for
social status, perfection, or concealment of their illicit behaviors. In one prominent case, she infiltrates a school obsessed with academic perfection, where students go to extreme, murderous lengths to secure top ranks. Nanno encourages this cutthroat ambition, ultimately leading the entire student body to tear itself apart. In another harrowing arc, she exposes a seemingly wholesome, progressive school that actually harbors a dark history of student abuse and institutional corruption. By manipulating the desires of both the abused and the abusers, Nanno orchestrates a systematic breakdown of the school’s facade, forcing the perpetrators to face poetic justice.As the series progresses, Nanno’s methods evolve, testing the boundaries of human morality and questioning whether people are inherently flawed or simply corrupted by their surroundings. She occasionally faces challenges from rival entities, most notably Yuri, a resurrected mortal who survives one of Nanno’s trials and gains similar immortal, chaotic powers. Unlike Nanno, who maintains a detached, karmic neutrality, Yuri revels in bloodshed and seeks to overthrow Nanno by encouraging even more brutal, irreversible acts of vengeance. This dynamic introduces ideological conflict, as Yuri believes humanity is entirely beyond redemption and deserves swift, merciless destruction, whereas Nanno prefers to let humans self-destruct through their own conscious choices.Throughout the narrative, Nanno operates without emotional attachment, vanishing just as mysteriously as she arrives once a lesson is taught and a life is ruined or transformed. The overarching plot does not follow a linear progression of Nanno's personal backstory; instead, it builds a sprawling anthology of human depravity. By the end of the journey, the series cements its premise: Nanno is not a creator of evil, but a relentless mirror reflecting the deepest, darkest impulses of humanity back onto itself, proving that monsters are rarely supernatural, but rather manufactured by society.