^ It kind of is and kind of isn't.
Kuro was the original personality of Ilya - Ilya was born to become the holy grail (kind of a super powerful magic ritual) - but her parents decided to to not go through with it and to raise Ilya as a normal girl so magically sealed / put to sleep? that personality and most of the power when still a baby - and the current Ilya's normal personalty developed.
Unbeknown? to everyone the original personality was still there / was aware to some degree / and grew up in her mind / spirit or whatever. Once Ilya became a mage, though most of her power was sealed with Kuro?, it awoke Kuro a little? and when Ilya was in great danger she manifest and Ilya kinda turned into Kuro for the fight a few times.
Anyways to cut a long story short, Kuro ends up separated via magic from Ilya, as a real physical being and living in the real world - though she is kind of a being created of magic and needs regular / weekly? infusions of magic to not die -done via kissing - and by far the most compatible is Ilya ofcourse :)
So you see it's kinda complex lol - they later live together and call each other sister, which they kind of are - but she is also kind of Ilya too - or a different version of her who would of been the one and only, if her parents went through with their original plans. But she is her OWN Ilya - Kuro has a very different personality.)
I might of got some of that a bit wrong (not a huge Fate series fan besides Ilya show so not up on all the lore from the wider story / world) but that's basically it.
last edited at May 10, 2017 1:10AM