Umineko no Naku Koro ni takes place primarily in the year 1986, during the time frame of October 4 and October 5 on a small, secluded island named Rokkenjima 10 km around owned and lived on by Kinzo, the head of the wealthy Ushiromiya family. Kinzo is near death, and eight of his family members arrive on the island for the annual family conference, where the adults plan to discuss how Kinzo's assets will be divided once he is dead. Also on the island are three family members who live there, five of Kinzo's servants, and his personal physician. After the eight family members arrive, a typhoon traps them on the island, and shortly after, strange things start to happen and people start dying.
The main character of the story is Battler Ushiromiya, son of Kinzo's second son Rudolf. Battler has not been to the annual Ushiromiya conference in six years due to living with his maternal grandparents ever since his mother Asumu died, and even took his mother's maiden name instead of Ushiromiya. When his grandparents died, he went back to living with his father, his second wife Kyrie, and their daughter Ange, his half-sister. Once on the island, Battler once again becomes acquainted with the legend of the golden witch Beatrice who supposedly lives in the naturally dense forest on Rokkenjima. A portrait of her lies in the entrance hall of the Ushiromiya family mansion, and a puzzling epitaph is written below the portrait. Rumor has it on the island that Beatrice gave ten tons of gold to Kinzo in the past to restart the Ushiromiya family after being crippled in the 1923 Great Kanto earthquake. It is said that whoever solves the riddle of the witch's epitaph will receive the gold and be the next successor to the Ushiromiya family.
Once the typhoon hits, a ghastly game begins, starting with the murder of six people on the island. If the witch's epitaph cannot be solved, people will continue to die in mysterious deaths, following the outline given by the epitaph itself, until the witch Beatrice ultimately revives. After this comes to pass, Battler is the only one left alive who does not believe in witches or magic, and as such the door to the "golden land" (as stipulated on the epitaph) cannot be opened. Beatrice takes Battler and herself to a parallel dimension, Purgatorio, which is able to oversee events on Rokkenjima. From this point on, Battler and Beatrice are locked in a game of twisted logic where Battler must attempt to explain all of the mysterious events on Rokkenjima from the standpoint that they are caused by a human, and Beatrice attempts to explain everything with witches and magic. One of the recurring motifs is use of the locked room mystery, and several logical arguments are presented to explain the mysteries including the devil's proof, the raven paradox, and Schredinger's cat. If Beatrice can get Battler to ultimately surrender and accept witches and magic, Beatrice wins.
This story has the part which was created by referencing Wikipedia, so the licence of GFDL is applied to this story.