I'd be lying if I said Emi was spawned rather spontaneously. Salt got creative and I'm happy that he did of his own accord. I managed to cook up some lore about her on the fly and I'm glad it turned out that way. I felt Kuroba was missing an element to his part of the story. I don't want him to play second fiddle to his sister. I can already imagine quite a few hijinks involving himself and Emi.
Imagine what would happen if I wrote a side story about him bringing her to Universe 9 for a visit? Imagine the possibilities.