Board Thread:Boruto: Naruto the Movie/@comment-27162446-20151105015144/@comment-24808887-20151202223126

^It is hinted in manga actually Kakashi said something like: "Not even Sharingan can see it all" to FRS in Hidan and Kakuzu ark wich most likely means that there is limit to eyes on how many targets they can follow and at how much speed it can be done.