Subaru was born in Kyoto on 19 February 1974, the younger of a pair of fraternal twins, his older twin being a girl named Hokuto. Their parents (who are never seen) were members of the Sumeragi, a clan of onmyouji who have served Japan and its emperors for hundreds of years.
Subaru was trained from an early age to become the 13th head of the Sumeragi clan, replacing his grandmother. At the age of nine, he was separated from his sister Hokuto for a year of intensive training in Tokyo. On the day he ascended to the head of the clan, Subaru encountered a strange young man under a cherry tree. The meeting would subsequently be expunged from his memory.
Subaru's grandmother ordered him to wear gloves from that day onwards, and never to allow anyone else to see his hands. The old onmyouji cast a spell that would repel any attempts by others to remove them. Subaru never removed his gloves, and was known to wear them even when sleeping.