Being in the same hemisphere as us in the UK, Japan is best to visit in September, December or April for a sports tour.
For history or cultural tours, however, any time of year is fine and the cherry blossoms in spring are spectacular.
Japan is a land of amazing contrasts: from the fast-paced and thriving Tokyo to the ancient cities of Kyoto and Osaka. There are hot springs (that the monkeys also enjoy), you can stay in a traditional Ryokan, see magnificent Mount Fuji and visit ancient temples and beautiful forests.
In Tokyo you might like to visit the Sumo Museum, Disneyland, the Meji Shrine and also shop for electronics!
Japan can be expensive, especially in Tokyo, but a variety of rail passes on offer and accommodation in traditional Ryokan style hostels can make it an affordable destination.