Japan needs to test a nuclear warhead. We already know they are 30 minutes from being nuclear capable. They need to up the pressure with a 5 megaton test. Normally I would say 0.8-1.2 megaton test but China and NK keep pushing. I would be ok with 10 megs. It’s academic at that level.
Second thought, a joint Japan, South Korea, Taiwan test would be stellar. That would be awesome.