I have been reading that in Japan, the standard electrical outlet only has 2 prongs. In the USA, we have some 3 prong devices. I see many places reference getting a travel adapter which convert 3 prong devices to a 2 prong. Can a simple grounding adapter like this on work in Japan? Assuming the voltage level is correct.
In Japan, on the outlets near the area where one would plug in a refrigerator or washing machine, there is a flap at the bottom which if you lift up reveals a screw that sandwiches two copper plates (that are then linked to ground.) So you just loosen the screw and wedge the tongue plate in and screw it back down.
You just need to add this cord to your cheater plug to be able to do the above dance:
But in general, grounding systems don't work in Japan anyway. The land mass of the islands is too small to sufficiently take up the misdirected electricity.
It's unclear if that adapter has polarized prongs (one bigger than the other). If it doesn't, it will work. If not, you'll have to find one that is not polarized (i.e. both flat pins are the same).
Also keep in mind that the electronics you plug in will need to have a converter built in. Ones that do will say something like ~100-120v, ~50-60Hz.
When I went to Japan in March we came up with a great solution to the problem that is the voltage is the same, but the plugs don't have a grounding pin (so laptop AC adapters wouldn't work). I went down to the dollar store and bought a cheapo power bar, took a pair of pliers and ripped the ground pin off the power bar, and pronto, had a very cheap multiple device adapter for all my grounded stuff.