The Kuwadorian (九羽鳥庵 lit. Nine Birds' Retreat?) is the second mansion on Rokkenjima. The Kuwadorian is where Beatrice Ushiromiya was held for a majority of her life. The Kuwadorian is secluded far away from the Ushiromiya main building in order to keep Beatrice hidden.
The existence of the Kuwadorian was revealed in Banquet of the Golden Witch.