In Japanese society, it is said a curse is created when a person dies in the grip of a powerful rage (emotion) or sorrow. Those who encounter the evil supernatural force are consumed by it, the curse is born repeatedly and spreads. The original victims of the curse, the Saeki family, haunt their Tokyo suburban house as ghosts and kill anyone who enters. Housewife Kayako Saeki was murdered by her husband Takeo Saeki after he discovered she infatuated to another man, their son Toshio Saeki and pet cat Mar also being murdered, before Takeo was hanged by Toshio’s ghost. In the first film, American social worker Karen Davis tried to burn the house down to stop the curse, but failed, finding herself hospitalised and haunted by Kayako. The film's chronology is told in a non-linear fashion, taking place in 2004 and 2006 respectively.
The Grudge series focuses on those affected by a curse created in a house in Suginami by a deceased family's rage that destroys the lives of everyone who comes in contact with it. Known as "the ju-on," this curse causes its victims to become fatally afflicted with it, which in turn leads to a new curse being born and passed like a virus to all those who enter the family residence or come into contact with the curse in any way.