Tactics
Although a Servant of the Assassin class, he does not employ assassination techniques such as ambush, instead frequently choosing to fight face-to-face. During battle, Assassin counters the opponent’s attack with sword techniques and Eye of the Mind, or simply by dodging. If he detects an opening, he would decapitate the opponent with the 5-shaku katana with certainty. Also, Assassin can deliver slashes even while standing idly, without assuming any stances. His technique is extremely swift, and very difficult to read. Kojiro Sasaki’s ultimate weapon is the technique that has reached the pinnacle of training and approaching True Magic --- Tsubame Gaeshi. It is an attack that delivers 3 slashes simultaneously, enough to overwhelm even Artoria.

Fate/complete material III; Servants of the Fifth Holy Grail War, pg. 34-35