Hansuke Doi

Age: 25
Birthplace: Fukuhara (current Kobe)
Job: Theory teacher, Class 1-Ha
Committee: Explosives Committee advisor

The main classroom teacher for Rantarou and his classmates. The class causes him a lot of stomach aches and worry, and he often loses patience with his students due to their inability to pay attention or remember the theory he's thought them. However, he's very well-liked by his students, and he doesn't take kindly to anyone else looking down on them. Theoretically skilled with explosives and strategy, though in reality he often ends up taking down opponents using school supplies such as chalk, blackboard erasers or the attendance book instead of actual weapons.

Kirimaru stays with him during school holidays, and the two of them have become a lot like family.