Onigiri are rice formed into a ball or triangular shape, often wrapped with seaweed. They are a fast snack to eat on-the-go. When we eat rice at home, rice is normally served in the rice bowl, so rice-ball is a food to be eaten outside on occasions such as a picnic or trips.
Because of the popularity of rice-ball in Japan, most convenience stores stock their rice-balls with various fillings and flavours and today, rice balls are starting to change a bit as the younger generations take pictures of them for Instagram and other social medias to post. Rice-balls are changing into something photogenic, super colourful and in interesting shapes to get peoples attention.
Also, there are some onigiri cafes that have opened which is very interesting as I mentioned rice-ball is a food to eat on-the-go. We do have rice-balls as side menu in udon restaurants etc, but things are changing!
Common rice-balls are just filled with ingredients such as umeboshi plum, bonito flakes, grilled salmon and kombu etc, and these are some of the new generations of rice-ball today.
This is an onigiri with fillings popping up. How its made is, rice wrapped with nori and then cut slit just bit so you can put the filling there and it looks like the filling popping out. (photo from pinterest)
This onigiri is made using sushi nori, (a larger sheet than is usually used for onigiri), and this is not really like rice ball anymore, it's folded to sort of square shape and cut to show the filling. (photo from pinterest)
Hawaiian inspired rice-balls. The fillings that are used usually include spam, eggs, pineapple. (photo from Aloha Farm Cafe http://www.alohafarmcafe.com)
Cafe style rice-balls
It seems like the rice-balls served in cafe or onigiri restaurants, the fillings are placed on top of the rice balls so they look nice and people can take nice pictures of them. Also the filling they use are gourmet, they are cooked and have more flavour when compared to normal fillings like kombu and umeboshi. Some western ingredients are often used too.( Photo from Omusubi Zen http://omusubizen.com)