What you can have in Nagano prefecture
as an alternative to onigiri
Like onigiri, oyaki have a variety of fillings :b
An American friend of mine who had recently been in Japan told me of how she had "over-dosed" on onigiri when in the Land of the Rising Sun whereas our mutual Japanese friend who she was travelling about with over there never seemed to tire of the rice balls and could easily eat as many as four of them over the course of a single long distance train ride.
While I'm a fan of onigiri myself (and tend to also opt for them as my "go to" food on train rides and frequently too for breakfast when I'm in Japan), I could see how eating rice balls -- even ones with a variety of fillings (including ones as diverse as ikura (salmon roe), natto (fermented soybeans) and ume (plum paste)) -- every day on a holiday could get old after a while. So I was pretty happy to be able to try out a portable food alternative to them that's specific to Nagano prefecture on my recent Japan trip!
With a texture and shape somewhere between a Chinese steamed bao and a fried Japanese gyoza, oyaki are dumpling-bun thingies whose dough is made from buckwheat -- like the handmade soba that the area is known for, and also the seriously delicious as well as surprisingly filling galette I had at an eatery called Donguri House over by Togakushi's beautiful Kagami-ike! And while these rustic delicacies may not look all that stunning, trust me when I say that I could happily eat quite a lot (more) of them if I had spent more time in Nagano prefecture!
As it turned out, I "only" had some oyaki on three occasions during the four and a half days or so that I was in the part of Japan with which it's associated. And for the record: two of these were when I was on a train while the third was at a roadside stall when I was in the middle of sightseeing and wanted a quick rather than leisurely and/or super large lunch.
Although I've seen oyaki filled with red bean and even cream cheese, I tended to go for those sometimes steamed, sometimes baked affairs with more traditional savory fillings such as hijiki seaweed, kinpira gobo and spicy nozawana (pickled green vegetables). And while I'm definitely am an omnivore who loves seafood (especially sushi) and also a variety of meats (including pork, goose, mutton and beef), here's pointing out that I really do appreciate getting to include a variety of vegetables in my diet whenever I'm in Japan -- as well as being able to try a variety of often very local regional specialties! :)