Hiraga Gengai

Japanese name:

平賀 源外

A genius robot builder with the tile Edo's Greatest.

SpoilerIn Episode 17 of the anime he helped Takasugi try to assassinate the Shogun with his robot Saburo (whom he named after his son) during the festivals fireworks. Reason being that his son, also a genius inventor who was stationed in Takasugi's troop during the Joui War and getting killed on the battlefield.

Seiyuu: Aono Takeshi

Wikipedia