Nice thread and all, but one thing you must realise is that Kishi always like hyperboles in this manga. One day he says one thing and tomorrow you see the counter. Like he said Gaara's sand was the ultimate defense, yet Lee countered it. Like he said Susanoo was the ultimate defense, yet we saw that underground was the weakness. Like he says in his databook that Amaterasu burns at the same temperatur as sun, but we all know that it's impossible, or everyone around it would have been desintegrated in an instant.
If we go by that logic, must i say that Raikiri can pierce thru Yata mirror then? After all Raikiri's databook says it pierces thru everything:
Databook1 said:
The one who is said to have copied over 1000 jutsu, Kakashi's single original
technique, this is "Raikiri"! Gai says that the true nature of this technique is
"a regular stab", but the amazing time when you see this huge amount of chakra
is gathered in the hand, Kakashi's arm becomes a famous blade that can cut
through anything.
Even Gai said it in the manga
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If we go by the databook3, when Kakashi wasn't able to use his kamui perfectly, Kamui is the ultimate technique and against this technique no defense is possible(yata mirror included?)
Databook3 said:
Kakashi's original doujutsu, released from the "Mangekyou Sharingan". It allows one to transfer anything to another dimension. If one spends a lot of time and trains one's chakra over and over again, this technique can be invoked. The target is enveloped with a barrier space, and the user concentrates their mind to what they gaze at... The target can struggle helplessly, but against this technique no defence is possible. No matter what, the space will distort and draw the target in.
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↑When the technique is invoked, the space at the centre of the barrier is distorted and the target inside the barrier is drawn in completely... There is no technique that can compete against this one.
On the second bold part, you even see him saying that there is no technique that can compete against this one. And it's validated when Kakashi said Kamui is unstoppable:
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If it is true,
does it mean that Kakashi is invincible right now?