There are two modes in Japan that get a lot of use and that is 1.2Ghz FM and SSB in the VHF/UHF bands. 6M SSB is also a big mode and many hams will use the HB9CV antenna.
The Japanese have a profound interest in the outdoors, not just because of Mt Fuji but because there are coastal areas and mountain areas in Japan that are just as beautiful. Take a look at Snow Peak which is the iconic outdoor brand in Japan and this neat Field day set up
Due to the relatively small 4 tatami apartments and condos in Tokyo, many hams take to the outdoors to enjoy fresh air and dx the bands ham rover style. Kenwood TS811 and TS711 are the most popular rigs.
We visited Mt Fuji in May and there was a lot of snow on the slopes and the time we got there it was freezing, overcast and about to rain. This was the highest we could go due to the poor weather conditions.
Here is Takashi JA1QPK antenna farm up 4 floors. Comet and Diamond antennas are his friend. There are many hams with this set up which explains the weaker signals coming from Japan.