|Anime debut||Yu-Gi-Oh! SEVENS episode 03232: "The Lady Who Loves Her Heavy Cavalry"|
Tadashi is an old man with hazel eyes, grey hair that is styled in a similar manner to his great-granddaughter's, and darker grey eyebrows and an arrow-shaped moustache. He wears a thick grey jacket over a white-collared shirt and a black tie, white gloves, thick orange-brown pants tucked into black boots, and a yellow hardhat while operating R6 with the Mutsuba Heavy Machinery logo stamped on it.
Tadashi took Asana riding in R6's bucket one day and showed her Goha City, explaining that Mutsuba Heavy Machinery had constructed the city and given rise to mobile Duels using R0, though it had gone missing and everyone now used Goha Enterprises's Duel Disks. He also told Asana that the founders of Goha Enterprises and Mutsuba Heavy Machinery were close friends who Dueled every day, a relationship Asana likened to her friendship with her great-grandfather. Tadashi introduced Asana to Haruka Kamijo, whose family owned the Kallister Gear Company. One day Asana called Tadashi to bring R6 to look for Haruka's younger brother Lucidien after he went missing, but they instead found Chevelle Kayama and Trapigeon beneath the snow. They then learned Lucidien had been found, so they took the weakened Chevelle and Trapigeon to the hospital. Tadashi later passed R6 on to Asana. Mutsuba Heavy Machinery eventually fell on hard times and was absorbed into Goha Enterprises, reducing the once proud company to a simple bicycle store.
Goha 6th Elementary
Asana made several attempts to have the parts of Heavy Cavalry remanufactured, including making a deal with Goha Enterprises to crush the Rush Dueling format, but she eventually failed and R6 was destroyed. Her opponent, Yuga Ohdo, found R0 in the Mutsuba family's mine and convinced Asana and the Heavy Cavalry Duel Club to accept the idea of modification given that R0 had been modified during its construction. As a result, Asana allowed Yuga to repair R6 at Tadashi's bicycle shop, a feat that impressed Tadashi.