On the Other Side of Lies and Façade - S2.E6

Miyu and Kuro have an intense battle before Illya arrives to try and stop them, apologising for the words she said before. When Irisviel suddenly arrives to pick Illya up, Kuro tries to attack her, but she stops her with her own magic. Irisviel reveals Kuro was sealed away so that Illya can become the Holy Grail, with Kuro becoming upset when she learns the Holy Grail War no longer takes place, feeling she has no place to belong. She ends up overusing her mana and starts to disappear, but Illya gives her some of her own mana so that she can last longer. Told by Illya to make her own wish come true, Kuro wishes to have a family, allowing her to come back into existence as a proper member of Illya's family.