He is Class 3A's teacher. Rei Miyamoto is afraid and is disgusted by him and Saeko Busujima says his name with a scowl, showing that he apparently is a sadistic and villainous character. Both girls have good reasons to do so as we see him leaving behind a student who has sprained his ankle and even kicking him back towards a group of zombies chasing them. He then makes 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 with glee. It is assumed that the former's story is true because he pointed the nail gun at Shidō without blinking or hesitating to punch a nail wound to his face.

He has a desire to be a leader and some of the characters have theorized that he is trying to build a new religion with him on top as leader. Shidō is an apparent coward in the face of extreme danger, as seen when being threatened by a grazing head shot with a nail gun on Hirano's part, but nonetheless, proves to be a manipulative, villainous and sadistic character.

He is last seen by the main group when they abandon him on the bus, leaving him with only those willing to follow him. He reappears once more and is seen watching over an orgy between his followers on the bus at the end of Chapter 11, in a sort of Charles Manson-ish brainwashing (he allows his followers to do as they will, calling it "free time"). He seems to have a spy inside the base of humans set up at the mansion, who, as of Chapter 12, is relaying vital information about the morale of the people there. He is seen to keep his followers in line through intimidation, forcing them to follow him lest they incur his wrath or be left to fend for themselves. He sees the people that follow him as angels that will help usher in a new age, since they are youthful teenagers. Shidō then accuses one of the teens on board the bus of showing weakness, the boy having shown concern for the welfare of his family. He convinces the rest of the group to eject the 'weak link' for the sake of the New World. Highlighting how far Shidō has turned the minds of his followers, they callously throw the teen off the bus, going so far as to bid him farewell as he attempts to get back on the bus, only to fail and be subsequently attacked by a zombie. The teen is later seen in his undead form in chapter 15 when the dead break into the estate.

Later on, his history and background with Rei was shown when his father was involved in Japanese politics and had Rei retained as a favor of getting back at his stepbrother. When threatened with a rifle-mounted bayonet by Rei, he seems scared witless until he realizes that no one would come to his aid before daring her to kill him. When she turns away and says that he is not even worth killing, his fury is shown. He is seen being ordered to leave the estate with the students he brought but ends up crashing into the forklift when the EMP Blast temporarily stopped the bus, removing the concrete blocks which served as the barrier against the undead. He recovers consciousness in time to see the undead horde advancing through the gap in the barrier. He is later seen at the elementary school where the evacuation is taking place.

Source: Wikipedia