Good one.
Amaterasu works instantly [
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Even perfect Sage's can't react to the instant of Amaterasu. Sasuke cast Amaterasu right at Kabuto's feet, without killing intention [
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]. He could have aimed at Kabuto's body as well if for the killing intent. You see how the flame appeared right before Kabuto and see Kabuto in the middle panel braking before running into the flames.
It's annoying to discuss
common things with members who don't have an idea about the subject matter.
You need Raikage A's speed to dodge Amaterasu, that's how this technique was portrayed. Anything else is bs.
The sensing of Sages is based on the increased perception ability, as Kabuto stated. Naruto stated that he can feel danger better. That doesn't help against Amaterasu, as demonstrated at the fight with DSM Kabuto, who almost ran into an Amaterasu, which was cast before his feet without killing intent. He didn't even have any facial expression telling us that he saw it coming.