Originally Posted by Vengeance
When did he claim that? MS wasn't a concept in the manga until the end of part 1.
After Naruto came back from his training at the very beginning of Part 2, Kakashi offered to show him his "new technique" that he had developed during the timeskip. Naruto turned him down and ran off. Later Kakashi used his Kamui against Deidara. Considering that's the only completely new move he's been shown using post time skip it's safe to say that's what he was referring to. I believe kakashi said something later on when he talked to Itachi about his MS, asking him how bad had his eyesight become.
This is where the plot hole comes in. After getting MS the eye slowly starts to become blind. Using MS techniques put extra strain on the eye and speeds up the process greatly as was the case with Itachi and Sasuke. If kakashi got his MS as a kid, then that means he's had it over twice as long as Itachi had his. Itachi didn't spam it even near as much as sasuke did and he still managed to go completely blind in about 5 or 6 years. Now apparently Kakashi's had his for 16 years and not only isn't blind but isn't even close. Even after using Kamui almost a dozen times all together. 3 times against Deidara, a few against Pain, 2 or 3 times against sasuke, and now his fight against Tobito. How is he not blind!!! It makes no sense.