Hideo was born in Matsumoto, Nagano, Japan, along with his younger brother, Suhara. As they grew, Hideo was the more scholarly and responsible sibling, while Suhara was the exact opposite. They lived a simple and poor life that Hideo was content with. However, Suhara believed he deserved more, so he decided to become a thief. Hideo became curator of Matsumoto Castle's museum, and one night, Suhara, who had joined the Yakuza, stole the katana of a legendary samurai's daishō as an initiation, but before he could steal the accompanying wakizashi, Hideo thwarted him and Suhara fled with the stolen sword, therefore severing his relationship with his brother.
Many years later, Suhara, now Shadowsan, returned the katana he stole and apologized to his brother, prostrating himself as a sign of remorse. However, Hideo rejected his brother's apology and Shadowsan left.
Hideo would later return in the episode "The Masks of Venice Caper", attending a special exhibition of rare and valuable masks from around the world in Venice, Italy as a guest speaker. He was instructed by museum security, as well as ACME agents Chase Devineaux and Zari to watch for any suspicious activity, as there was a risk of thieves attempting to steal the masks. He was then shown an image of Carmen, whom he recognized, as well as sketch of Shadowsan.
That night, he interrupted Carmen and Shadowsan as they attempted to steal the masks from the museum, where Carmen attempted to defend Shadowsan, informing him that they were only taking the masks to protect them from real thieves. However, when shown a video of Mime Bomb, Hideo did not believe that he was a thief, believing that the two were attempting to distract him while a cohort stole the masks, pointing out that Neal the Eel had arrived and was currently doing so. However, upon witnessing Shadowsan attempting to protect the masks from Neal, he began to believe them, but did not think that stealing the masks were the only way to keep them safe. When Shadowsan told him that it was the only way they knew, he offered to help, knocking out Zari with a velvet rope post when she cornered Carmen and Shadowsan. He then aided in lowering the crate filled with the masks to a waiting boat, after which Shadowsan advised him to leave so as not to be noticed by the authorities.
After the masks were secured by the proper authorities, Hideo stated that his brother was performing "A samurai's work in ninja's clothing", and stated that he could not welcome Shadowsan back home, as he still had important work to do with Carmen and her team. The two bowed to each other, their family bond at long last restored.