I agree that they are Chinese more than Japanese. But there are
more kinds of dumplings than potstickers... (Japanese name is gyoza,
and they have a flour dough base, you can get pretty close results
with the premade fresh wonton or spring roll wrappers you can buy in
the produce sections sometimes).
There are also lighter (more translucent) rice-flour steamed dumplings.
Usually stuffed with shrimp but the other day, I had some stuffed
mostly with spinach and water chestnuts that were really nice....
They are served usually at dim sum places, the shrimp ones I think
may be called (apologies for my poor Chinese) har gau. Perhaps you can
look in Chinese dim sum cookbooks for the dough recipe. I like the dough
on these much better but no idea how to make them.