The Japanese are known in the world today for their pacifist approach to everything, so when you take that into consideration what kind of percentage of Japanese people are actually willing to go out and fight for their country?
The actual figure according to surveys is as low as 11%, which is the lowest in any country in the world. It really is to do with their approach to anything of this ilk so it is perhaps not as surprising as it would be if that figure was seen with other countries.
At the other end of the scale, people in Morocco and Fiji are seen as being the most patriotic in this sense as the same survey showed that 94% of the population were more than happy to pick up arms and defend their country if asked to do so. Clearly, they do not have the same pacifist culture as you find in Japan.