Shimizu is an isolated and ignorance coward who doesn't have friends. He doesn't cares of his teacher or classmates. He wants to kill his sensei and classmates to destroy Heiligh Kingdom in sake to become a "Hero". While holding his teacher hostage, he demanded Hajime to give him his guns only the latter refused to give him and shot him by unknown assailant. While dying, he beg Hajime to spare his life to do what he says.
In his tragic past, Yukitoshi was an otaku. However, he had a miserable life when he was bullied back at junior high school for unknown reasons.
- Yukitoshi Shimizu has similarity to Benedict Arnold (the biggest traitor of America's history).
- Yukitoshi is one of the five of the classmates (except for Kaori Shirasaki who was revived) who died (along with Reichi Kondou, Daisuke Hiyama and Eri Nakamura). He was one of the two killed by Hajime Nagumo (other being was the zombie Reichi Kondou.
- He was the classmate who died first.