WHAT NO... it is undetectable the victim will NOT know they are being controlled and it is 100% unbreakable... Itachi realized it because he programed it to do so
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No, that's the problem I did read the manga.
Shisui uses KA to try and stop the coup, somehow fails.
Danzo uses KA on mifune, mifune told of it no longer wants Danzo to be the candidate. Simply knowing he was under KA broke its effect.
Crow uses KA on Itachi. Itachi knows of KA, the genjutsu still works but Itachi is able to disregard the command by knowing KA is being used on him.
Every time we have seen KA, the command has failed. I'm not going to say KA wouldn't one shot most people, but if you have seen shisui's and his eyes ability before, KA isn't going to work. It could possibly work on people if they knew about shisui and if the eye was hidden and they don't have byakugan or sharingan to see the eyes chakra, like it was with Danzo, but KA isn't hidden in Itachi's crow.