“From their conversations, as a Master, Ryuunosuke does not have any prior knowledge about Heaven’s Feel. Putting that aside, he doesn’t even have the self-consciousness of a magus.”

“This is quite possible. Under accidental situations, it is possible for someone without any magecraft teaching to make a contract with the summoned Servant… That Master will be the Servant’s puppet.”

- Fate/Zero: Act 5, Part 3