Unified NE Asian Kingdom (Japan + Korea + Mongolia) Options

[cyon]

I believe this idea was first brought in by many Japanese and Korean politicians about 4-50 years ago...

What do you think of the idea? Agree or disagree? Please answer (Japanese only!)

[Suijen]

^ There would need to be a strong reason for Japan and South Korea to unite. Mongolia is really too small, population and economy wise, to really be in the same league as Japan and South Korea. Thus, the only thing feasible would be something between Japan and South Korea, which is kind of confusing because most groups tend to have more than two members, and there needs to be a stated objective and Raison d'être that for existing (as well as for choosing members).

The ASEAN group was created to strengthen SE Asia against alignment in the Cold War.
The SCO was developed to link energy networks in China and central Asia.
The EU was created to develop greater economic integration and competition between the EU and the rest of the world.

A common currency would be a satisfactory reason, but it'd be odd if it didn't include China since China is such as important market for S. Korean, Japanese, and Mongolian goods, though I can kind of imagine something forming around the ASEAN + 3 group.