Giyu grew up alongside his older sister, Tsutako Tomioka. When he was still a child, his sister sacrificed herself to protect him from the Demons.[1]

After the death of Tsutako, Giyu tried to tell others that she was killed by a Demon, however, he was labeled as mentally ill and was sent away to one of his relatives, a doctor. Giyu ran away during the journey there and almost died on a mountain, but he was rescued and became apprenticed under Sakonji Urokodaki.[2]
His friend Sabito died.