Mitsuo is a second-year high school student of Prefectural Sanada North High School. He is in Class 2-A. An honest and naive person; Mitsuo is shown to have a caring side when he jumped into a river without hesitation in order to rescue a cat, which turned to be a stuffed toy. Despite all this, he is the butt of many jokes and pranks by his classmates and is often talk about with ridicule even in his presence. Some events of Yoshitake’s embarrassing childhood are even misattributed to him. Notably, everyone refers to him with the honorific "-kun."

He initially played soccer but later lost his confidence when he was unable to score a goal against Hidenori. Subsequently, he became a regular player of the rugby team. He also had a porn collection that his parents discovered.