Japan is made up of five islands Hokkaido, Shikoku, Kyushu, Okinawa and Honshu. Honshu is the biggest of the islands and it's where Tokyo is and most Japanese people live. Honshu is about 88,997 sq miles (230,500 km²) about 60% of the total area of Japan.
Hokkaido can be pretty cold and can get a lot of snow in winter, the further south you go the more tropical. Okinawa is hottest and has quite a bit in common with Hawaii - they both like spam (the meat not the mail). Okinawa is the biggest consumer of spam outside the states!
The population of Tokyo is about 8 million, London is 7.5, New York is about 8 million too. The population density of Japan is 836 people per square mile. The UK is 650 people per square mile and the United States is 84 people per square mile.