Assassin (Fate/stay night)

Assassin is a villain from Fate/stay night who is the solitary Servant of Caster during the fifth Holy Grail War.

Clothed in a traditional Japanese umanori hakama and kimono with an indigo haori, he bars entry beyond the main gate of the Ryuudouji Temple. Quiet and composed, he maintains a degree of bushido and is eager to spar with other Servants. While he is of the same class, he is not to be confused with Zouken Matou's servant, True Assassin.

Identity
Unlike other Servants, Assassin actually has no true identity, even though he masquerades as the mythical Japanese swordsman, Sasaki Kojirou. Although his name remains, he is a skilled swordsman whose actual existence is doubtful. He is a handsome swordsman who carried a 90cm (150cm in Fate/stay night) long blade, Mono-hoshi-zao. He was born sometime during the Eiroku era, and he is said to have become famous around the 10~17th year of the Keichou era, but the truth is in fact unknown. Books that included Sasaki Kojirou's name all contradicted each other in terms of years, and he hasn't even mentioned his biggest rival, Miyamoto Musashi's book, "Gorinn no sho." It is according to records that Kojirou was born in Echizen, he studied the Tomido style, a favored long blade, and, after defeating his master's younger brother, he named his style the Ganryu. Afterwards, he traveled around the country and developed Swallow Reversal as his secret sword technique, which could even kill a flying swallow. He later frightened the warriors all around the country, fought Miyamoto Musashi on Funajima in order to maintain the pride of his lord that he fought for, and died. He was unable to fight holding his sheath due to the length of his long blade, so he threw his sheath aside during his battle with Musashi, but Musashi saw that and said, "Kojirou, you lose. If you're were planning to win, why did you throw away your sheath?" Though Kojirou was Musashi's rival, his figure in Fate/stay night is as illusionary as the moon appearing on the water's surface. There was supposedly a person like him but we have to say the story of Sasaki Kojirou today was made up by people.