Umineko no Naku Koro ni takes place in the year 1986 during the time frame of October 4 and October 5 on a secluded island named Rokkenjima. The head of a wealthy family named Kinzo Ushiromiya, who lives on and owns Rokkenjima, is near death, and eleven of his family members arrive on the island to discuss how Kinzo's assets will be divided once he is dead. Also on the island are five of Kinzo's servants, and his personal physician. After the eleven family members arrive, a typhoon traps them on the island and shortly after people start to get mysteriously murdered.
While resting, the absent nurse returns to the office to finish the job she had failed the night before: suck Yoriko clean of blood. In the middle of the struggle, Kirin comes to save poor Yoriko from the demon nurse.
Turns out Kirin and her brother Koryu are 'oni'.