Minasan Konnichiwa,
Sorry my computer doesn’t have Japan entry, apologies for that.
Hope all is going on well~
I’m the host of Japan RR:
https://community.postcrossing.com/t/japan-other-countries-rr/1128/
We have many interesting groups, and we always welcome participants from both Japan and Other countries, we run small and fun groups with different topics, each group has one Japan member and 3 OC (other countries) member, Japan member send/rec 3 cards, OC members send/rec 1 card.
We also welcome host groups, where Japan/OC offer their own cards and state number of participants, requests etc.
We have well-established rule to run this RR properly since 2015 ^^ So you can join with peace of mind 
Welcome to join!! If any questions feel free to PM me any time.
Best regards,
londonbunny