Rokkenjima is a fictional island owned by Ushiromiya Kinzo, the patriarch of the extremely wealthy Ushiromiya family. It is small and secluded, and lies off the coast of Japan. Rokkenjima measures roughly 10km around and is covered mostly by forested areas, save for the mansion grounds as well as the grounds of a smaller, separate mansion. The design of the exterior of the main mansion's guest house is based on a mansion in Kyū Furukawa Gardens in Kita, Tokyo.
Once a year, the members of the Ushiromiya family (save for Natsuhi, Krauss and Jessica, who live on Rokkenjima along with Kinzo) travel to Rokkenjima for an annual family meeting. The 1986 meeting is the setting for the brutal murders which take place.
Banquet of the Golden Witch
In "Banquet of the Golden Witch", the existence of a smaller mansion called Kuwadorian on Rokkenjima is revealed. In the year 1967, Kinzo had managed to trap Beatrice in a human body and seal her memories. The human Beatrice lived in Kuwadorian alone. Rosa chanced upon this mansion one day, and invited the human Beatrice out of the mansion to "see the outside world", only to have the human Beatrice fall off a cliff and die. Upon her death, Beatrice regained all her memories and powers.