It would be very easy to assassinate an apprentice magus like Waver once his hiding spot became known – however, he could only make his move once Saber had lured away the opposing Servant. Kiritsugu had also followed Tōsaka Tokiomi, who had left Fuyuki Church by himself, all the way to the Tōsaka house last night, but hadn't found any opportunity to strike. He had felt Archer's surveillance over the situation from some unknown location. If he had boldly struck his Master under such conditions, it would have been nothing short of suicide.

- Fate/Zero: Act 13, Part 2