But the question is... When a Mangejyou user loses the eyesight completely, is he still able to control the Kyubii? And how about Kakashi's Mangekyou? Does his interdimensional abilities count as Suusano or the Kyubii control counts as such?
Maybe the way of obtaining the mangekyou is not exacly killing the best friend, but something else, that is accomplished as result of it, but not exclusively by it.