Hokuto Sumeragi

Tokyo Babylon: Hokuto is Subaru's twin sister. She is constantly teasing her brother about his relationship with Seishirou, and always has some crack about a wedding, which Seishirou always joins in on. She has an eye for fashion, and makes the most elaborate costumes.
X: Here she appears in flashbacks of the memories of Subaru, Seishirou, and Kakyou Kuzuki. ~!7 years ago Hokuto was killed by Seishirou Sakurazuka as exchange for her brother's life. However her last spell has to be fulfilled...!~

Her name, Hokuto (北斗), is the Japanese name for the constellation Ursa Major, whose brightest seven stars form the Big Dipper (Hokuto shichisei); it complements her brother's name, Subaru being the Japanese name for the Pleiades star cluster (whose brightest stars resemble a smaller version of the Big Dipper).