Outside of North Korea diplomacy,... did we learn anything about other diplomatic issues like Japan?

Not so much, at least on the surface.
That's one shortfall of the president's trip this week.
There was no visible contact at all between leaders Moon Jae-in and Shinzo Abe although both were at the General Assembly.
The presidential office reportedly said that discussions with Japan are underway behind the scenes, but there's been no concrete outcomes or progress just yet.
But here are two key dates the top office considers as potential dates that could trigger a turning point.
October 22nd. The Japanese emperor's enthronement ceremony.
And November 22nd.
The termination of the military intelligence-sharing pact with Japan... called the General Security of Military Information Agreement, or GSOMIA for short.
So if the behind-the-scenes discussions in fact make progress,... the top office reportedly anticipates the leaders of the two sides will meet face to face perhaps on the sidelines of multinational meetings like ASEAN in Thailand.
A lot to look forward to for South Korea and its diplomacy.
Thank you.