During the Kouran Invasion, in the 7 Years War, all the Koutoushu were seemly exterminated. The proof of a Koutoushu, the bladeless sword, the Dragon Sword, hasn't been seen in a long time. The royal family of Nil Kamui were all Kotoushu and therefore the survivors of the 7 Years War, Ibuki and Inori both have the supernatural power and are both entitled to the position of King and the Throne of Nil Kamui.