The Preliminary is the ceremony of passage to obtain the right to participate in the Holy Grail War.
The Preliminary takes place in an artificial “what if” world that is made to reflect Japanese high school student life as it was around the turn of the 21st century.
The magus who were summoned to the Moon have their personality temporarily sealed away, and they attend Tsukimihara Gakuen as regular students.
While living a normal life, only the students who are able to restore their personality are allowed to proceed to the Holy Grail War tournament.
Once the Preliminary is determined to be over, the students who have failed to restore their personality are deleted along with the school buildings.
The Preliminary takes place in a loop world without a start or end.
In EXTRA the Preliminary takes place over four days.
In CCC the Preliminary takes place over just one day, but that’s because the setting is a loop world designed to allow the protagonist to sleep peacefully.