the last time we saw kakashi using kamui was against tobi and he was going to kamui him imediatelly untill tobi said that it's doesn't works on him.
funny how kakashi underaters and want restrict kamui to not use at beginning ...
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if he can kamui an arrow of susanoo of the size of 3 human body tehre is no reason that he can't,furthermore the head or any vital point is enough,andagainst deidara he needed preparation and was the first time he used it on a fight, the target was very high and far,flying and escaping and kakashi was still able to take 1 arm ,don't underestimate him.
he don't need time to activate it,he was able to kamui a susanoo arrow of the size of 3 human body in a fration of second.
the arrow was launched directly towards him so of course he can kamui something like that, but theres no proof that kamui can actually teleport a full human body