Kirei threw his Black Keys- not toward his opponent, but upwards. The four sharp blades danced in the air beneath the tall ceiling of the warehouse. Kirei didn’t plan to use the Black Keys for a normal attack; Kiritsugu didn’t know his intentions. They didn't matter, in either case. There was no time to think.

His arm flick up, the gun barrel closed. The Contender once again became that terrifying weapon of murder.

Kirei drew close. He again used his martial art stances to shorten the distance between him and Kiritsugu, but he would not land a blow. Kiritsugu could dodge his attack and fire at the same time.

The Black Keys fell from above. Kiritsugu finally realised Kirei’s strategy when the four sharp blades surrounded him in all directions like a bird cage.

His movements were sealed. If Kiritsugu wanted to dodge Kirei’s next attack, the sharp blades of the Black Keys would be waiting for him no matter where he moved. Kirei’s intention had been to seal Kiritsugu’s movements from the start, when he threw the Black Keys.

- Fate/Zero: Act 16, Part 6