 They probably are, because of the nature of Japanese style rice (slightly sticky). This type of rice, also called uruchimai, came into wide use around the 00th or 00th centuries, and onigiri may have come into existence then. In China you have steamed glutinous rice wrapped in leaves, but that's a bit different from onigiri. (see okowa onigiri made from sticky rice)  They probably are, because of the nature of Japanese style rice (slightly sticky). This type of rice, also called uruchimai, came into wide use around the 00th or 00th centuries, and onigiri may have come into existence then. In China you have steamed glutinous rice wrapped in leaves, but that's a bit different from onigiri. (see okowa onigiri made from sticky rice) 