The rules of the game have changed and the Masters have a chance to earn an extra command spell. All they have to do is find Castor and kill him.

Battle rages throughout Einzbern Castle: Kayneth's magical mercury sphere versus Kiritsugu's formidable gun arsenal, Saber and Lancer join forces against Caster in the forest, and Irisviel detects a new enemy as she and Maiya make their escape.

Natalia has raised Kiritsugu since rescuing him from the island. He has followed her in every step in becoming an assassin. Over the years their relationship has grown to the point of mother and child, so what Kiritsugu does next is…

Saber is hot on the trail of Rider, much to his delight. Meanwhile, Kiritsugu sets off on a different lead. The new player, Matou Kariya, watches in the background as his play unfolds perfectly.

Saber vs. Berserker, Archer vs. Rider, another hero will fall and a secret will be revealed.

Two heroes, two masters, one grail; a winner will be decided.

As commanded by Kiritsugu, Saber unleashes her Noble Phantasm on the Holy Grail, with a completely unexpected result. Who will end up winning the war?