Fate/Hollow Ataraxia [Type-Moon]

Bazett Fraga McRemitz, a member of the Mages’ Association and a master in the 5th Holy Grail War, wakes on the fourth day of the 5th Holy Grail war with a new servant, Avenger, and no memory of what happened to her beforehand. She and Avenger set off to fight and win the Holy Grail…