There, the Moon Cell orchestrates a replication of the Holy Grail War using a system called Serial Phantasm or SE.RA.PH, which handles the summoning of Servants.
The world is set in a school called Tsukumihara Academy, a fictional place existing within an artificial environment called the Moon Cell. As of the 2030s, the world's mana was completely gone.
The universe of Extra shares the events of the Fate/stay night universe until a 'certain major incident' in the 1970s that caused the world's mana to start drying up causing it to split off into its own separate universe.
