In the midst of the Fifth Holy Grail War, Caster sets her plans into motion, beginning with the capture of Shirou's Servant Saber. With the witch growing ever more powerful, Rin and Archer determine she is a threat that must be dealt with...

Eons ago, a cube–like peaceful planet named Quarton, populated by shape–shifting living bricks called Tenkai, was ravaged by a war between two opposite factions: the Corekai and the Corrupted led by the ruthless warlord Vilius...