On the eve of the Fifth Holy Grail War, unusual agitation was reported in the spiritual veins of Fuyuki City.

Rin Tousaka, a young woman who bears the honor of her family and the pride of a magus, chants the spell to summon the Heroic Spirits in her ancestral workshop. What she seeks is a sword sharp enough to sever her fate, a key to the "root."

However, the one who descended was the alien Herrscher who was supposed to dissipate in the cocoon of the end— "Nice to meet you, my dear little Master! Just call me Alicia♪"

The pink-haired, pointed-eared girl landed gracefully on the ground, holding a crystal longbow, with a sea of ​​stars in her eyes.