Category 1: A group of 20-30 people suddenly remember their past lives in which they interacted with one another as either allies or enemies.
Category 2: A significant amount of the the world's population suddenly remember their past lives; in which they interacted with one another as either allies or enemies.
Category 3: The same as Category 1 but the past lives of these people are of fantasy worlds instead of real world eras of the past.
Category 4: This same as Category 4 but the past lives of these people are of fantasy worlds instead of real world eras of the past.
–
These stories cannot end with a twist that the people were only perceiving fake memories which was created by some government experiment.
by Axer51