Nope, they would fight each other
Yes, they would help each other
Well they would need the us, but yes they would help each other.
East Asians dont like each other. Chinese hates koreans who hates japanese who hates the vietnamese etc. They never get along.
They're nothing compared to China, they'd need to help each other.
I don't see why not. They share similar ideals and have a common link (the US) when it comes to military alliances.
Japan doesn't have a military, you idiots. So they would have to have the U.S. help them, but the U.S. wouldn't want to fight against SK -__-