Kirei Shared Perception

While his eyes were closed, he was not resting but sitting in silence with his nerves on edge. The jet-black figure was Kotomine Kirei's priest's frock.

From his profile, one might think that he was contemplating about certain matters. Who would have thought that he was listening to the crooning of the sea breeze, and seeing before his eyes a battle scene full of the sparks from the clashing of steel.

What he was seeing and hearing was an unknown battle between Servants taking place in the distant warehouses… the contents identical to those seen by his Servant Assassin.

He was using the result of his past three years of study. An ability called Shared Perception that was taught to him by Tōsaka Tokiomi.

Using only a prana connection, he was able to share senses with the one that made a contract with him. In the Heaven's Feel, the ability to completely monitor a Servant's actions from long-distance is very useful. If one's Servant is Assassin, who is especially skilled in reconnaissance, then the ability is peerless.

The only difficulty lies in that if the contractor does not agree to it, the ability can not be used. For Tokiomi, who taught this magecraft to Kirei himself, his suggestions were immediately rejected by Archer. For the haughty King of Heroes, even if it were his Master, to allow another to look through his eyes seems highly unlikely.

Therefore, the only ones who can achieve this are Kirei and Assassin.

- Fate/Zero: Act 3, Part 4