During the Fifth Holy Grail War, while servants and masters are being contracted, Tokiomi Tohsaka's firstborn child and real heir to the Tohsaka family magecraft, Tohsaka (y/n) leaves the Mages Association Clocktower in England and comes home to assist her younger sister, Tohsaka Rin to win the war. The girls team up with the master of Saber, Emiya Shirou, and agree to go into the madness to identify how to make Fuyuki safe once again without too many casualties and also, how to save Her youngest sibling, Matou Sakura.