What Do You Put Inside An Onigiri?

What Do You Put Inside An Onigiri? Tuna Mayo (Sea Chicken, シーチキン・ツナマヨネーズ) … Grilled Salmon Flakes (Yaki-shake/Beni-shake, 焼鮭・紅しゃけ) … Pickled Plum (Ume, 梅) … Salted Cod Roe (Tarako, たらこ) … Dried Bonito Flakes (Okaka, おかか) … Kelp Simmered in Soy Sauce (Kombu, 昆布) … Grilled Salmon Cream Cheese (焼サーモンクリームチーズ) Does onigiri need filling? Onigiri do