Iō (イオウ, Iō) is a ninja weapon inventor from Konoha. He and his assistant, Shōseki, help make weapons for the village.
Most of his original weapons are shown to either be impossible to carry or serve no purpose at all. It is assumed he was relocated to the outskirts of the village due to the random explosions he creates, which he claims are "challenges" during his inventing.
Iō has a very eccentric personality and has a great love for creating weapons without thinking of the consequences, even creating weapons that were either impossible to use because they served no purpose or were too "over-the-top". He is also shown to resent not being able to experiment with his creations. Despite being relocated and not allowed to pursue his experiments within Konohagakure, Iō has shown great loyalty to his village, refusing to make or give his weapons to anyone else.
Iō is a small, balding man with grey hair, a small moustache and goatee. He wears a pair of gloves with bandages around his arms, a high-collared jacket, black trousers, sandals and a blacksmith'sapron with the village symbol on it.
He is very knowledgeable in the art of creating ninja tools, able to create unorthodox yet dangerous weapons like Tsurukame, Dakō or Jidanda, showing a high level of technical knowledge. However, most of these unorthodox inventions are useless for combat. He has also shown rather skilled at laying traps, as well as proficiency with the Enclosing Technique, using it to store some of his creations.
Past Arc: The Locus of Konoha
Neji Hyūga, Tenten, and Naruto Uzumaki go to the Konoha Tool 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 in 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 then took Jidanda back from Tenten after the ninja were defeated, saying more work needed to be done on the weapon.
Three years later, Tenten and Neji Hyūga return to the research lab to retrieve more tools for the village after its destruction.