Japan is a somewhat isolated island culture. The world looks interesting. Many Japanese people are eager to see it.
Domestic travel (in Japan) is expensive. It's cheaper to go to Hawaii than to stay at the hotel down the street.
Domestic shopping (in Japan) is expensive. It's cheaper to fly to Paris to buy a few Louis Vuitton bags than to buy them in Ginza.
Japanese people tend to be brave travelers who go virtually anywhere around the globe.
Japanese companies give short but frequent holidays. Japanese workers never get two weeks off. However, if you add up all the holidays they can take over a year its comparable to the best countries in Europe. As a result Japanese tourists tend to take many short trips of 3 to 5 days.
Japanese tourists are popular with hotel owners around the world who consistently rate them as the most polite, trouble free guests.
The large numbers of Japanese tourists visiting popular destinations in Europe and America can cause some friction with the locals. Japanese tourists commonly note that they face discrimination and mistreatment in certain cities in Europe.
The negative stereotype of the clueless Japanese tourist with thick glasses and five cameras is well known in Japan.