Giyu grew up alongside his older sister, Tsutako Tomioka after the two were orphaned. When he was still a child, his sister sacrificed herself to protect him from the Demons. giyu has choppy raven-black hair of uneven lengths, with jaw length side-bangs, a low messy ponytail at the base of his neck, and bangs falling over his eyes in a choppy fringe. His eyes are sharp and moderately large, having irises a lapis blue color, and their pupils a navy blue, sometimes having his irises completely opaque and empty, just in lapis blue color, and are framed by thin eyebrows.

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 by a demon hunter and became apprenticed under Sakonji Urokodaki.

Giyu was thirteen years old when he met Sabito he was a fair-skinned young man with a large scar running from the right corner of his mouth to his right ear, and kind, cat-like eyes of a grayish lavender color, a horizontal bar of much paler purple visible across them near the bottom. He had thick, spiked, peach-colored hair of varying lengths, the longest reaching his shoulders, that he wore messily down with side micro bangs over the left of his forehead. while training under Sakonji, and they became good friends due to their similar pasts and age. Sabito and giyu were lying on the grass together and sabito smirking and show his teeth Nevertheless Even though they both had the same background, at least Giyu had a close friend, at least he wasn't alone They were students of Sakonji Urokodaki and they were both taking a break after a long training period.

Sabito: "Look, isn't it a beautiful day today? We took a break after a long training session. Especially the sunlight comes here and makes it bright."