what are the countries included in northeast asia?

Answer 1

I hope this site helps http://en.wikipedia.org/wiki/North_Asia

Answer 2

Honestly, I have not heard the term NE Asia used before, at least in the media and I do reside in SE Asia. They usually classify Asia, as North, Central, and SE Asia.

North would be the former Soviet Union, so now would include maybe Mongolia, Siberia and Russia. There are still disputed territories that both Japan and Russia claim as there were before WW2 or the Pacific War.