“? . . . What could that be? I had a feeling I just sensed something nasty.”
“Sure it’s not just your imagination?” Prelati chimed in from beside the confused Francesca as he stuffed his face with sweets.
They had activated two illusions inside Kuruoka Tsubaki’s ward-world using the Noble Phantasm Grand Illusion.
First, they had tricked the ward-world itself in order to trap Saber and Ayaka in an isolated space. Second, they had cast an illusion to trick Saber and Ayaka’s five senses. Saber and Ayaka were currently seeing a vision of Fuyuki. It was as if they were decked out in VR gear from head to toe.

Fate/Strange Fake: Volume 6, Chapter 20 ("Dream Becomes Reality")