He is the teacher of Class 3A.
Rei Miyamoto fears and despises him, while Saeko Busujima mentions his name with a scowl, indicating that he is a sadistic and villainous character. Both girls have valid reasons for their reactions. We see him abandoning a student who has sprained an ankle and even kicking the injured student back towards a group of pursuing zombies. He then delivers a speech about how weaklings do not deserve to exist. It was implied by Hirano that Shidō allowed bullies to beat him up as he watched gleefully. This story's credibility is supported by Hirano pointing a nail gun at Shidō without hesitation or blinking before punching a nail wound into his face.
Shidō harbors a desire to be a leader, and some characters theorize that he aims to establish a new religion with himself as its leader. He reveals cowardice in extreme danger, such as when threatened by a near-miss head shot from Hirano’s nail gun, yet remains manipulative, villainous, and sadistic. The main group abandons him on a bus, leaving only those willing to follow him. He reappears later, overseeing an orgy among his followers on the bus, reminiscent of Charles Manson's brainwashing tactics (he allows his followers to act freely, calling it "free time").
It is suggested that he has a spy within the human base set up at the mansion, relaying crucial information about morale there as of Chapter 12. He maintains control over his followers through intimidation, forcing them to obey under threat of his wrath or abandonment. He views his followers as angels ushering in a new era due to their youthfulness. Shidō accuses one teen aboard the bus of weakness for showing concern for his family, convincing the others to eject this 'weak link' for the New World’s sake. Demonstrating their altered mindset, they coldly throw the teen off the bus, bidding him farewell as he fails to get back on and is attacked by a zombie. This teen is later seen undead in Chapter 15 when the dead invade the estate.
His history with Rei is revealed, involving his father's involvement in Japanese politics and retaining Rei as revenge against his stepbrother. When threatened by Rei with a rifle-mounted bayonet, he initially appears terrified until realizing no one will help him, daring her to kill him. Her refusal leaves him furious. He is ordered to leave the estate with the students he brought but crashes into a forklift when an EMP blast temporarily halts the bus, removing the concrete barrier against the undead. Regaining consciousness, he sees the undead horde advancing through the breach. Later, he is seen at the elementary school where the evacuation takes place.
