When Subaru's sister Hokuto is killed by the man he loved, Seishirō Sakurazuka, Subaru goes on a quest to confront the assassin.
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Subaru and Hokuto are good friends with a kindly and magically-aware veterinarian named Seishirō Sakurazuka, whom they met at a railway station after Subaru's shikigami led him on a bizarre chase.
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In Tsubasa: Reservoir Chronicle, Subaru reappears as one of a pair of twin vampires alongside Kamui Shirō for whom Seishirō Sakurazuka is searching.
He lives in Tokyo with his twin sister Hokuto, an exuberant girl whose chief occupations are to design eccentric clothing for herself and her brother, and to egg on their mutual friend Seishirō Sakurazuka, a kindly, 25-year-old veterinarian, when he declares his love for Subaru.