Fate/Extra

Waking up in a strange virtual world with no recollection of the past, the main character (Hakuno Kishinami) finds themselves forced to fight for survival in a war they do not understand for a prize beyond value; the opportunity to have one's wish granted. With only an enigmatic "Servant" by their side, the protagonist will have to face both friends and foes in battles to the death in order to gain possession of a mysterious object known as the "Holy Grail." (wiki)