Ep 15. Princess of Colchis

Shirou and Rin finally find a moment of peace after the grueling events of the last episodes. As they walk through the city, Rin reveals to Shirou that her father had connections to the Holy Grail War and that she is now the head of the Tohsaka family, responsible for continuing the legacy of magecraft and protecting the city from harm.

Meanwhile, Archer and Saber continue their search for Caster and her Master, encountering a powerful Servant who quickly overpowers them. After barely escaping with their lives, they regroup with Rin and Shirou to come up with a new plan. Rin decides to confront Caster directly, hoping to negotiate a truce to end the war peacefully.

As Rin and Archer make their way to Caster's stronghold, they are ambushed by a group of powerful demon Familiars. Rin uses her magecraft to fend them off, but Archer is gravely injured in the process. Just as they are about to be overwhelmed, they are saved by a mysterious woman with exceptional magecraft skills.

The woman reveals herself to be Medea, the former princess of Colchis and Caster's true identity. She offers to help Rin and Archer negotiate a truce, but warns them that her Master is unpredictable and unlikely to agree to their terms. Nevertheless, Rin and Archer agree to Medea's proposal and make their way to Caster's stronghold once again.

When they arrive, they are greeted by Caster's Master, a ruthless and sadistic man who revels in the chaos of the Holy Grail War. He refuses to negotiate with Rin and Archer, instead attacking them with all the power at his disposal. The battle is intense and grueling, with Archer and Rin each using their own unique skills to try and gain the upper hand.

In the end, the battle is won not through brute force, but through the power of words. Rin appeals to Caster's sense of honor and duty, convincing her to break free from her Master's control and join forces with the other mages to stop the war. Though her Master is enraged at this betrayal, he is quickly defeated by Berserker, who has been silently watching the battle from afar.

With the peace restored, Shirou and Rin finally have a moment to reflect on their journey so far. They realize that, despite all the hardships, they have become stronger and closer as a result of their experiences. With the Holy Grail War drawing to a close, they prepare to face whatever lies ahead with newfound determination and resolve.