Blue Glass Moon - S3.E6

Having completed reconstruction of her mansion, Luvia invites everyone over for a house party, after which the girls discuss their plan to obtain the eighth card. As the girls prepare for what could be their final mission, Kuro questions Irisviel over how the cards are related to the Holy Grail War, which involved only seven classes. Ruling out the possibility of Irisviel being involved, Kuro suggests that they question Miyu, but Illya feels it is best to focus on the task at hand and find the answer themselves.