Kouichi Shidou is introduced as the homeroom teacher of class 3-A at Fujimi High School, but beneath a composed and cultivated demeanor lies a deeply manipulative and sadistic personality. He is the son of Ichirou Shidou, a prominent member of the House of Representatives, and his family background plays a crucial role in shaping his warped psyche. His mother descended into alcoholism and died, and when his father chose a stepbrother to inherit the family political base instead of him, a profound hatred for the entire Shidou household took root. From that point, he outwardly adopted a facade of obedience, secretly working to bring ruin to his family name. While many at the academy initially view him as a model educator and a person of upstanding character, a handful of students and staff are keenly aware of the malice he projects.

His personality is defined by cold-hearted cruelty, contempt for weakness, and a yearning for absolute control. He openly articulates the belief that weaklings do not deserve to exist, a conviction he demonstrates early in the outbreak by callously kicking a student with a sprained ankle back toward approaching zombies and leaving him to die. He is also shown to have taken pleasure in allowing bullies to torment a student, watching with glee. Despite his arrogance and grandiosity, Shidou reveals cowardice when faced with genuine lethal threats, yet even then he remains calculating, using intimidation and rhetorical skill to reassert dominance. He harbors an unsettling fascination with young women, and his vision of a new world order includes a loyal following that indulges his desires.

His primary motivation is to seize the catastrophic collapse of society as an opportunity to crown himself the leader of a new age. He does not simply want to survive; he wants to reshape the world according to a twisted doctrine where he stands at its apex, revered like a religious figure. This drive leads him to rapidly transform into a cult-like figure among the students who escape with him, brainwashing them with charismatic speeches that blend promises of salvation with fear and moral corruption. The pursuit of power also intertwines with his personal vendetta against his father’s legacy, making him see the apocalypse as a chance to finally overturn the order that rejected him.

Shidou’s role in the story is that of a major human antagonist whose actions rival the horror of the undead. He first appears as the class teacher who boards an evacuation bus with the main group. Almost immediately, he installs himself as the de facto leader, turning the vehicle into a mobile microcosm of his ideology. The core survivors quickly recognize his danger and abandon him along with those who have fallen under his spell. He resurfaces later having intensified his hold over his followers, running the bus as a debased commune where he orchestrates orgies and demands absolute obedience, resembling a Charles Manson-style brainwashing operation. He places a spy inside the mansion shelter used by the main group, sows discord, and forces his followers to expel a teenager who shows concern for his family; the boy is callously thrown off the bus and devoured, later returning as an undead threat during a breach at the estate. His eventual crash into a barrier during an EMP-triggered catastrophe does not end his influence, and he is last observed at an elementary school evacuation site, still clinging to his delusions of leadership.

Key relationships orbit around fear, hatred, and psychological conflict. Rei Miyamoto is visibly terrified and disgusted by him, a reaction rooted in a past entanglement where his father used her as a pawn in a scheme against the family, leaving her deeply scarred. Saeko Busujima reacts to his name with open scorn, and Kouta Hirano has personal reason to despise him because Shidou encouraged his bullies. When Shidou threatens Hirano, the usually meek boy does not hesitate to fire a nail gun at him, grazing his face. Later, when Rei levels a bayonet-mounted rifle at him, he dares her to kill him, only to become enraged when she deems him not even worth the act. These encounters highlight how he feeds on fear but crumbles when his authority is utterly dismissed.

Throughout the narrative, Shidou evolves from a seemingly ordinary teacher into an increasingly unhinged demagogue. Early scenes present him as a smooth-talking figure who merely takes charge in a crisis, but his methods quickly escalate to overt psychological terror and ritualistic control. The longer the outbreak continues, the more he discards the mask of civility, openly reveling in the depravity of his followers and the suffering of those he considers weak. Even when physically removed from the main group, his shadow looms through his spy and the consequences of his manipulations, making his progression one of deepening corruption and entrenchment in his messianic fantasy.

Notable abilities center on his oratory skill and psychological cunning. Growing up as a politician’s son gave him a sharp understanding of how to sway a crowd, exploit fears, and project authority. He uses rhetoric to reframe survival as a spiritual calling and to justify atrocities as necessary steps toward a purified new world. His talent for intimidation keeps his followers obedient, while his ability to read and exploit vulnerabilities allows him to insert himself into power structures and destabilize rival groups. These traits make him a persistent threat even without physical prowess, turning the collapse of civilization into his personal stage.