You forgot to add logic to this post. Kakashi can set up Kamui even faster than Susano arrows, which are way faster than kunais. Hashirama wont be on time to throw the kunai. Please stop posting nonsense.
Why are you out of all people talking about "add logic to the post".. when only thing you to defend the 3rd raikage is wank over fan-fic durability , that most of the people who surpport you can't even prove.. including you.
Now for the main topic.
Kakashi cannot set kamui faster than Hashirama can throw a kunai, the Kunai's purpose isn't to hit Kakashi, its to distract him and than Hashirama pops a Mokuton in near instant.
Do you know how fast a Perfect susanoo sword slash is? faster than the susanoo arrow, especially when swinging down. rofl. Hashirama stopped it near instantly at a very very close range.
You are acting like the moment the fight start Kakashi will kamui the first second, because thats not happening.