there was a thread about orange mask obito vs. Danzo. everyone was for obito. when some was for danzo he said Koto Amatsukami -> make obito kill himself.
But know i thinking about what if someone knows about koto amatsukami? and knowing its about the enemy is controlling you without knowing that you are under the genjutsu.
but does fact that you know that the enemy might already control you and let you do things you would never do (suicide) make you snap out of KA? or just do nothing and overthink every action you gonna do. obito would have time for it while hiding in kamui dimension.
one question is if this is even possible (making ka effectless)
the other question is we dont really know if obito might know about shisuis ultimate genjutsu.(he knows pretty much stuff)
same goes for itachi. he knows about koto amatsukami (fact) would he able to get out if ka?
but even if this is possible: 1. you need good selfcontrol and good thinking. (always questioning and overthinking
2.it will definitivly (is this the right word?) slow you down -> ka would be still usefull