Arc 23The Sea Monster and the Betrayal
Jeanne gathered the factions to stop Gilles de Rais, whose return led to a battle against a monstrous being from another world. As the creature was defeated, Kotomine Kirei killed Tohsaka Tokiomi and tried to claim Gilgamesh, but Matou Zouken seized the contract through Matou Kariya.
- Diarmuid lost to the King of Rome’s giant-tree Noble Phantasm, while Lainas made Miss Sola Lancer’s new Master and Jeanne learned that children led the Black Faction.
- Jeanne confronted Gilles de Rais, destroyed his workshop with the Flame Holy Sword, and saved the still-living Assassin, who turned out to be Karen’s familiar companion.
- Rin discovered that Sakura was a Master and learned that Tohsaka Tokiomi had signed the contract that sent her to the Matou family, while Gilgamesh helped Kirei accept his true nature.
- Jeanne suspended the Holy Grail War and gathered the factions to hunt Gilles, while Bai Yue located him at sea and helped Jeanne lure him out.
- Gilles sent a colossal alien creature toward Fuyuki, and the two Sabers destroyed its monsters as Caster and Kayneth fused into a regenerating creature.
- Assassin attacked the sea monster while its mental contamination drove the Archers toward madness, and Matou Kariya left the battle to confront Tohsaka Tokiomi.
- Kirei stabbed Tohsaka Tokiomi and framed Matou Kariya, then formed a contract with Gilgamesh before Matou Zouken took control of Kariya and seized the connection.