>Assassin's skill as a swordsman

Nasu: This Assassin, or "Kojiro Sasaki", could possibly the most skilled swordsman in the history of mankind. He was the kind of guy who would hide himself away deep in the mountains and spend his days swinging his sword, with little interest in anything else. But he never desired or attempted to show his hard-earned sword skills to anyone. The popular notion that there are more people like him in this world than most realise took form as "the hope of the people" and produced sword skills capable of contending with Noble Phantasms.

Fate/complete material II; Characters: Assassin, pg. 88-89