I had almost lost interest in the show but now its picking up its mystic effect. Kanji's returned and brought around a fresh wave of mystery.
I think its a daughter that Kanji handed over and it will be Santo.
Somehow in the series, I have never found any of the sister's surname mentioned with such stress as Santo's. Although its not a logic that has much base to it, it still can be a possibility.
Santo can be Kanji's daughter but might not be Moti's daughter.
Just a thought.