There are different selectors available for each force. This is a Bolt Action thing - you use a different army list if you're doing, for example, French forces during the Battle of France rather than the Vichy French forces in North Africa, so there are different selectors for each. So there's not a single Japanese list, there are several you can choose from.
The Easy Army site lets you pick one of those selectors, then choose the units you're going to use for each, and it works out points costs and stuff for you.
In almost all cases, you need to take an officer and 2 infantry teams before you're able to take other stuff, and you're limited on the other stuff you can take.