Kirei dodged the upward stab as the dagger was removed from its sheath, and used his left arm to block the downward slash and backhand horizontal swing Kiritsugu followed up with. However, with these three attacks, Kiritsugu shifted around to Kirei's left hand side, into Kirei’s blind spot. As long as he stayed on the left side of the enemy, Kiritsugu would have all the chances in the world to strike Kirei down from his blind spot.

Kiritsugu’s sharp blade sliced closer, but Kirei didn’t turn; instead using the left side of the body to block every swing. Turning would have been pointless; his broken right arm could not possibly block Kiritsugu’s dagger. Thus, though it disadvantageous for Kirei to use his left side to defend himself, he had no other choices.

The dagger attacked continuously, flickering through the air with a chilling light. No regular human would have been able to even see Kiritsugu’s movements; only the lighting-like residual images the dagger left in its wake. Kirei, though, blocked every attack using just his left arm. Kirei, who easily defended himself even when faced with attacks made at three times the speed of normal humans, terrified Kiritsugu. There were a few attacks that even Kirei would never have seen coming with his eyes, but the Executor’s left arm defended him, as if it could see every swing.

- Fate/Zero: Act 16, Part 6