[Touko]

Originally Posted by mAc Chaos

I'm pretty sure that Kotomine mentions in FSN that he is basically contracted to the Grail like a Master, so it's more like he became it's Master since he accepted it.

Incorrect.

Spoiler:

Sakura was acting as Angra Mainyu's Master. Kotomine was just benefiting from the Grail trying to corrupt Gilgamesh. Because the Grail cannot corrupt Gilgamesh, all the power flowed through the leyline into Kotomine, reviving him. The explanation is in this scene:
http://fsn.seorinwastaken.com/archive/364.html