Mitsuo, referred to as 'Mitsuo-kun' by most characters, is a second-year student at Sanada North High and a member of Class 2-A. He is well-known in the series for having really bad luck and being naive, yet kind.
In junior school, Mitsuo was extremely gullible and believed in many outlandish things. As a result, he became the subject of various notable incidents that are still laughed about even when the boys are in high school. For example, Motoharu once switched his shoes with a girl's as a prank, but the two of them graduated elementary school without ever realizing it.
He also donned the mask of Rubber Shooter.
Mitsuo is of an average height and build. He has messy dark brown hair and brown eyes, and is usually seen in the North High uniform.
Mitsuo is a kind-hearted and friendly boy. Despite the fact that others usually have fun at his expense (including being insulted even when he is around at the moment), he is of a gentle disposition. He is shown to get scared (especially of cockroaches) rather easily and is sometimes overly dramatic.
He is famous for being gullible and being unable to pick up on basic cues, and usually has very bad luck. As an example, he bravely jumped into a river, intending to save a floating cat in a box, only to find a stuffed cat inside. Afterwards, his friends note that it isn't even the first time he's leaped into the river.
Mitsuo is very physically capable, having made it into the rugby team's playing roster. In one instance, he knocks down Motoharu by accurately and forcefully throwing a marble (a stone in the manga) at him from several metres away. He also stands his ground and takes on Yoshitake (of noted athletic prowess) and four others when they ambush him together.
- He fared well in the character popularity poll, coming in 12th place with 3,712 votes.