Kakashi can't copy Kekkai Genkai, like Susano'o, Rinnegan, Byakugan, etc. He used Perfecte Susano'o on his own, simple. I don't remember seeing anything that you need two EMS to get Perfect Susano'o. Also, note that this is Kishi's manga, I mean, if he really wants to, he could give Sakura the...