I’m not exactly sure how far in advance JL opens its schedule, but if you’re booking with AA miles you can only do so 331 days in advance, which means January 29, 2020, is the furthest out you can book right now. I see 2 J seats on HND-GMP on plenty of days in January 2020, including the 28th and 29th.

I don’t think JL even flies NRT-ICN any more.

The issue could be one of timing; given the arrival of the HKG-TYO flights, you might have to overnight in Tokyo.