The difference between a Japanese saw and an American saw is more than just the place of origin. Japanese saws have different teeth configuration, where the tooth will be cut in a diamond shape and how they are used. More specifically, a Japanese saw cuts on the pull-stroke, instead of the push-stroke with American saws. While the pull-push motion is the same, adjusting to the cut on the pull-stroke can take some time though with practice, it comes to feel quite natural.
Just like American saws, Japanese saws come in different forms and are used for different purposes. Below is a description of four Japanese saws: the dozuki, ryoba, keyhole and folding.
Dozuki: The dozuki is the equivalent of a back or tenon saw. The supported blade is approximately ten inches long with fine teeth, usually with more than twenty teeth per inch. As with all Japanese saws, its kerf is very narrow and it cuts quite rapidly.
The saw is most useful in finishing work, like cutting moldings, as well as one-repetition cutoff work, like cutting something into an oddball length like one-by-four, where it is more convenient to use a dozuki than to take the time to set up a power saw.
Ryoba: Unlike the dozuki, the ryoba has no American equivalent. Instead, it looks more like a weapon than a home-improvement tool, but it's a clever saw that can be very useful.
It has two sets of teeth on opposite sides of the blade. One side is used for crosscutting, with it containing 10-14 teeth per inch, with the other side used for ripping and has five to seven teeth per inch. The downside to the ryoba is that it is very fragile and becomes a radically different tool if stepped on. But if it can be properly protected, it is a useful tool because of its versatility.
Keyhole saw: The Japanese version of the keyhole saw has a finer blade than its American counterpart and also cuts on the pull-stroke. It's most effective at cutting holes with a very small radii, sometimes even smaller than the saber saw can cut conveniently.
Folding saw: The Japanese folding saw is probably the handiest of the Japanese saws. They are very useful to have on site, especially for one-shot tasks. Plus, when use is completed, the blade folds safely into its handle like an over sized jackknife and is small and light enough to be carried safely in a back pocket.
The teeth on a folding saw are generally coarser than on dozuki saws, but they are fine enough for trim work. The length of the blade varies depending on the model, but nine inches is common.