Been recommended to cancel my trip to Hong Kong next month so either looking at Seoul for a couple of days or straight to Japan and spend longer travelling around. Going to Asia at this moment isn't exactly the most comforting thing but we've saved and planned for 18 months since our wedding
My apologies if someone has already told you this, but if you are going to spend two or three weeks in Japan and you want to see as much of it as you can, you should buy a JR Rail Pass. They are a little expensive, but it will give you unlimited travel throughout Japan; travelling by train in Japan is much more comfortable and convenient than the UK. You can only buy it abroad, so you need to buy it before coming here.
Of course it goes without mentioning that you should monitor the Corona virus situation before coming here, but if you do decide to come to Japan, don't be unduly worried with everyone wearing masks; they do that every year.