Is very fast.
For those of you who doubted the speed of which Kakashi can could activate his MS:
Here, we clearly see his eye is in the 3 tomoe stage, but only 2 pages later [Must have been only a couple of seconds in real time] we see he has activated his MS WHILE doing a jutsu! [Showing that he no longer requires hand seals or a lot of chakra concentration to activate it.]
To sum it up, Kakashi is a beast.
He will only get better, and I think that not only will he reveal a new MS technique in this fight, he will also WHOOP on Yahiko's ass.
For those of you who doubted the speed of which Kakashi can could activate his MS:
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Here, we clearly see his eye is in the 3 tomoe stage, but only 2 pages later [Must have been only a couple of seconds in real time] we see he has activated his MS WHILE doing a jutsu! [Showing that he no longer requires hand seals or a lot of chakra concentration to activate it.]
You must be registered for see links
To sum it up, Kakashi is a beast.
He will only get better, and I think that not only will he reveal a new MS technique in this fight, he will also WHOOP on Yahiko's ass.