Often referred to as sour plums or Japanese apricots, Umeboshi plums are round, dried, and pickled fruits that have a distinctive sour flavor. These special plums are harvested in the summer season, ...

It uses umeboshi (salted Japanese plums), but what you put inside can ... Some people sprinkle their onigiri with sesame seeds. Oboro kombu, or shaved kelp, is another favorite.