Gyōgi was the great-uncle and teacher of Hamato Yoshi. He was well-versed in jūdō and was a Zen Buddhist. He taught Hamato Yoshi martial arts.
On August 6, 1945, while Gyōgi and 15-year-old Yoshi were out practicing, Gyōgi spotted American planes approaching. He sent Yoshi to warn the family, and when the atomic bomb dropped on the city of Hiroshima, Yoshi was safe, while Gyōgi watched the bombing directly and was permanently blinded by the flash.