Servant Summer Camp! Chaldea’s Thriller Night
The two Yu Mei-rens have a duel to determine who has to be Player 2. Then everyone prepares to fight Kiara after learning the true nature of her new form.
Full game playthrough: https://www.youtube.com/playlist?list=PLBC8w17FA1cv9oe63cGhYEhlaqyQxAl6v
Individual playlists by Singularity/event: https://www.youtube.com/user/pokedude9OO/playlists?view=50&sort=dd&shelf_id=6