The nineteenth person
The existence of a nineteenth person on the island of Rokkenjima is a recurring element in Umineko no Naku Koro ni. Initially, there are only eighteen people believed to be living on or otherwise inhabiting the island at the time of the Rokkenjima massacre; Kinzo Ushiromiya, Krauss Ushiromiya, Natsuhi Ushiromiya, Eva Ushiromiya, Hideyoshi Ushiromiya, Rudolf Ushiromiya, Kyrie Ushiromiya, Rosa Ushiromiya, George Ushiromiya, Jessica Ushiromiya, Battler Ushiromiya, Maria Ushiromiya, Genji Ronoue, Chiyo Kumasawa, Shannon, Kanon, Toshiro Gohda, and Terumasa Nanjo. Therefore, after the massacre begins, many characters believe there is a possible nineteenth person on the island who is committing the murders. The nineteenth person also represents a type of "holy grail" or ideal outcome for Battler: if he can prove the nineteenth person both exists and is guilty then he can simultaneously deny the witch Beatrice and avoid suspecting his friends and family.