Responses
He did something similar like this before when he was controlling Siwon's friend. I feel like this is partially Siwon's real memories and thoughts (just enough to make him doubt that this is fake) and part stuff Xuan is adding in himself
So were those documents actually his real feelings? We've known for a while that Xuan's stone lets him control the surroundings to an extent and I felt like he made that stuff up to brainwash Siwon into believing it. But how would he know about that night at the temple I wonder?