Banzou (蛮蔵), also known as mamushi no banzou (マムシの蛮蔵) is the originator of the Justaway explosive.
He used to work in a government office as a cop  but got laid off, and he became a terrorist in his bitterness. He started a factory, taking in displaced and bitter samurai who also wanted revenge. The factory acts as a front for the manufacture of Justaway, which is actually a bomb. Yamazaki Sagaru was sent to the factory as a spy to uncover more about the mysterious Justaway. It turned out that the factory also manufactured heavy artillery like the Mamushi-Z laser cannon.
- Sorachi Hideaki, Gintama, VIZ media, Vol. 7, Lesson 52, page(s) 52.