Assassin (Fate/stay night)

Assassin is a Servant in Fate/stay night.

Clothed in a traditional Japanese umanori hakama and kimono with an indigo haori, this handsome Servant bars entry beyond the main gate of the Ryūdōji Temple. Quiet and composed, he maintains a degree of bushido and is eager to spar with other Servants. Although he has the same class, he is not to be confused with another Servant known as True Assassin.

True Identity
Assassin has no identity, though he masquerades as the mythical Japanese swordsman, Sasaki Kojirō. The historical Kojirō was trained in the Chūjō-Ryū style of fencing, and also founded Ganryū, a school of kenjutsu. His weapon, Monohoshi Zao, is a sharp-edged and heavy nodachi, measuring at 90cm (150cm in Fate/stay night), an unusual length for such a blade.

Despite renown for his nimble footwork and mastery of kenjutsu, Kojirō is most famous for his death at the hands of Musashi Miyamoto, although some historians question whether Kojirō existed at all. Although he is mentioned in government records, there is discrepancy about his age, and Musashi does not mention a swordsman named Kojirō in any of his writings. In Fate/stay night, the profile of Kojirō in the modern era is an invention, a blend of details from the lives of many nameless and forgotten historical swordsmen. Assassin, a nameless wraith who shared similarities with the legend, assumed the appearance and skills of Kojirō upon his summoning.

Role
He was summoned by Caster as a guardian and watchmen for the front gate of the Ryūdō Temple. As an improper servant, Assassin is entirely dependent on Caster for mana and cannot move freely beyond the grounds of Ryūdōji. Furthermore, he lacks most of the usual parameters and abilities granted to his class. Because of his limited status, Assassin cares little for the Holy Grail, and outside of his duties to Caster, he only seeks to enjoy a decent sword fight. In the Fate scenario, Assassin drives back Saber during her first assault on the Ryūdōji Temple. During their second meeting (anime only), he allows Shirō Emiya and Rin Tōsaka to pass in order to engage Saber in a duel in which he is defeated. In Heaven's Feel, Assassin's flesh serves as Zōken Matō's catalyst for summoning True Assassin.

In Fate/hollow ataraxia, Assassin remains bound to the Ryūdōji temple, and continues to watch over its front portal even though peace has settled over Fuyuki City. He converses with whoever is nice enough to climb up the steps to see him. When Avenger makes his move, Assassins fights the dog-shadows right beside his Master, Caster.