I'm not going to say too much but, "However, because he is not an Uchiha, Kakashi is unable to deactivate it, keeping it covered until needed so not to risk his Sharingan using up a massive amount of chakra that would force him to take an extended bed rest. Because of this, Kakashi only relies on it when he feels it is an absolute necessity. Despite his handicap with the Sharingan, he is very skilled to the point that Itachi Uchiha acknowledges Kakashi's proficiency to most true Sharingan wielders"...
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ijs.