Iō

is a ninja tool inventor from Konoha. He and his assistant Shōseki help make tools for the village.

Background
Most of his tool creations are shown either be impossible to carry or serves no purpose at all. It is assumed he was relocated to the outskirts of the village due to the random explosions which he claims are "challenges" during his inventing.

Konoha History Arc
Team Guy (minus Might Guy and Naruto Uzumaki replacing Rock Lee) go to the Konoha Research Lab to retrieve more tools for the village. When checking up on their progress, they see that Iō and his assistant went down the research lab to work on Iō's newest weapon. Suddenly two ninja, Gameru and Kusune arrive to the research lab and demand new weapons from Iō. They both possessed two of his prototype weapons that Shōseki sold to them. Iō gave Tenten his newest weapon, Jidanda, which she used to defeat both the ninja. Iō took Jidanda back from Tenten after the ninja were defeated, saying more work needed to be done on the weapon. Years later, Tenten and Neji Hyūga return to the research lab to retrieve more tools for the village after its destruction.