Broom-head. Jirou is a wannabe school bully who was picked on when he was younger. When he arrived in Yagami, he vowed to become the top bully in the school; however, Harima being the top rival thwarted his plans. His story is illustrated in the first OVA episode. When his blonde hair is not slicked upward in his trademark broom shape, he wears it in two ponytails. This style matches Eri's, leading to occasional misunderstandings.
Jirou is a fan of the idea of "Swimsuit Sumo," and he seems to be quite talented at it as well, at one point winning a competition.