Subaru was born on February 19, 1974, in Kyoto, as the younger of fraternal twins. His older twin sister is named Hokuto. Their parents, who are never seen, were members of the Sumeragi clan, a lineage of onmyouji who have served Japan and its emperors for centuries. Subaru was groomed from a young age to become the 13th head of the Sumeragi clan, succeeding his grandmother. At nine years old, he underwent a year of rigorous training in Tokyo, separated from his sister Hokuto. On the day he became the clan's head, Subaru encountered an enigmatic young man under a cherry tree, an event later erased from his memory. From that day forward, Subaru was ordered by his grandmother to wear gloves at all times, concealing his hands from others. A spell was cast to prevent anyone from removing these gloves.
In 1991, Subaru had grown into a cheerful yet shy teenager, deeply dedicated to helping others both as Japan’s most powerful onmyouji and in everyday life. He exorcised demons, helped lost souls ascend to the afterlife, entered the minds of comatose individuals, and fought those who misused spiritual powers. Additionally, he stood up to bullies and provided comfort to their victims. Subaru lived in an apartment in Tokyo, sharing the building with his sister Hokuto, whose personality was the opposite of his—eccentric and outgoing. Hokuto often encouraged Subaru to think of himself more and criticized his excessive politeness, including his habit of bowing even during phone calls.
Subaru and Hokuto befriended Seishirou Sakurazuka, a kind and magically-aware veterinarian they met at a railway station. Seishirou acted as a guardian to both siblings and professed romantic love for Subaru. Although initially embarrassed by these claims, Subaru gradually accepted Seishirou’s affection. Subaru began recalling dreams about his ascension as the clan head, remembering a strange encounter with a young man under a blooming cherry tree. The man told him a Japanese folktale about corpses buried beneath cherry trees, dyeing the blossoms pink with their blood. Recalling this dream, Subaru wondered if the sinister young man could be Seishirou. Despite Hokuto’s suggestions linking Seishirou to the ruthless Sakurazukamori clan, Subaru dismissed it due to Seishirou’s kind nature.
After Seishirou lost the sight in his right eye protecting Subaru, Subaru realized he loved Seishirou. However, Seishirou revealed he was indeed the Sakurazukamori, incapable of love or hate. Lifting the veil on Subaru’s memories, Seishirou explained the bet they had made: if they met again, he would live with Subaru for a year to see if his heart could be moved. Seishirou claimed no emotions arose and attempted to kill Subaru, but Subaru’s grandmother intervened at great personal cost. Subaru fell into a catatonic state but recovered upon sensing Hokuto’s self-sacrifice to the Sakurazukamori.
Subaru dropped out of school to focus on his onmyouji training, becoming more reserved while continuing to help others. He took up smoking, mirroring Seishirou’s habits. By X/1999, Subaru was in his twenties, working under his grandmother’s direction. Recognized as one of the Dragons of Heaven, capable of creating kekkai (spiritual barriers), Subaru’s sole concern was settling his score with Seishirou. Encouraged by Sorata Arisugawa and Arashi Kishū, Subaru joined the Dragons of Heaven in Tokyo. He helped Kamui Shirou recover from a catatonic state and developed a close friendship based on shared hardships, acting as Kamui’s mentor.
Subaru faced Seishirou several times, each time spared despite being defeated. When battling Fūma, Subaru allowed himself to be blinded in his right eye, fulfilling a long-held wish. In a final confrontation with Seishirou at Rainbow Bridge, Subaru revealed his true desire: to be killed by Seishirou, believing it would ensure his existence in Seishirou’s heart. However, due to a spell cast by Hokuto at her death, the killing blow was reversed, and Subaru killed Seishirou instead. Seishirou’s last words profoundly affected Subaru.
In the manga, Subaru was slated to become the next Sakurazukamori, receiving Seishirou’s eye and completing the ritual. Unable to create kekkai any longer, his fate remains unknown as the manga is incomplete. In the TV series, Subaru sank into a catatonic state, urging Kamui to pursue his own wish. Eventually, Kakyou Kuzuki allowed Hokuto’s spirit to convince Subaru to rejoin the fight, leading him to protect Kamui from a fatal strike. Before his apparent death, Subaru urged Kamui to realize his wish, resulting in Kamui’s sacrifice to save humanity and Subaru’s revival.
In Tsubasa: Reservoir Chronicle, Subaru appeared as one of a pair of vampire twins, searching alongside Seishirou Sakurazuka. In xxxHolic, Yūko Ichihara mentioned knowing an onmyouji with a twin sister, referring to Subaru, hoping he would find happiness.
