Re: Naruto 620
Here is my take on Minato sensing abilities:
He like any other ninja that uses chakra can also sense it to an extent. Like when there is a huge amount of it any ninja can feel or sense it.
Also if the said chakra they sense is of a familiar origin, then they can say, "that is Naruto's chakra!"
So seeing as how Tobirama actually pinpointed where it was,that shows he is an ACTUAL sensor. Minato of course knew Naruto's chakra and the 9tails. But notice he could also tell that they were mixed together. Tobirama also only stated Madara's chakra, cause he knew that person.
Remeber in past fights with various characters when they fight someone really strong they may say," this chakra is ...." because they can feel or sense it to an extent. I mean how can you use chakra if you can't even feel it?
Don't bring up Lee, he uses chakra he just can't manipulate it for any jutsu.
So in the end, Minato is not a sensor he is just a ninja that knows familiar chakra when he feels it.
Why didn't. He know Obito you say? Simple: he was inside the Zetsu suit and Minato has NEVER met Zetsu or Hashirama before to say,"that is the 1st Hokage chakra. ..."
So.that is that, sorry I had to introduce logic into this. Just kidding, maybe.