I’ve been in Japan for the past couple of weeks and arrived in Asia via Hong Kong. What a fantastic country for SOTA where I climbed a few small summits but was no activating because I was not able to secure a licence.
There is currently a max limit of 100Wh battery packs per person and also a maximum of 2 battery packs on airlines/departures in Japan and also Hong Kong. They have to be in “small bag” hand luggage and within reach under the seat.
I was checked in HKG, OKA and KIX, because I have a 20Ah / 80Wh battery with me and also a 10Ah / 40Wh which was bad news. Thankfully my Daughter took responsibility for the smaller second battery packs !
Anyone arriving in the region should be aware of the limits. Airport security were enforcing them!