Ever wondered why onigiri are triangular? (Plus, unwrapping for dummies)

Written by
Joyce Lam

Originally posted March 12 2015

The staple ‘cheap eat’ of Japan, the onigiri is a snack, a fast food, an easy lunch. It’s the equivalent of that peanut-butter-on-white bread sandwich your mother used to put in your school lunchbox every day. Combining filling white rice and salty nori (seaweed), the onigiri is everyday soul food. But why are they triangular? And exactly when did the Japanese start making these rice balls?

Onigiris actually come in four different shapes but the triangle is the most common. Legend has it that travellers moulded rice balls into the shape of a mountain as a way of asking for protection from kami (spirits), which were believed by Shintoists to live within every element in nature. A more practical consideration is that the triangle shape is more space efficient and thus easier to carry around.


Often seen in the Tohoku and Chubu regions, these are rounded but flattened in the middle, making it easier to grill or wrap in leaves. It is more common to have grilled onigiris in Tohoku than in other parts of Japan.

The real rice ball, made by rolling in between the palms and most common in Kyushu and in parts of the Chubu region. Since it is simple to make, it became popular among commoners in the Showa period.

Sand bag
Most common in the Kansai region, the sand bag-shaped onigiri is a bulky pillar of rice. It is believed to have originated from the Kyoto Imperial Palace, where they called it ‘omusubi’, and became popular as it was easy to wrap seasoned seaweed around it.


The first onigiri
In 1987, clumps of carbonised rice thought to be from a rice ball were discovered at Ishikawa prefecture’s Sugitani Chanobatake Remains, which date back to the Yayoi period (300BCE-300CE). Apparently archaeologists even discovered imprints from human fingers on the rice grains. To commemorate the day this fossil was found, June 18 is now the official Onigiri Day.

First appearance in literature
Onigiri appeared as tonjiki (elliptical shaped rice) in the Japanese classic Genji Monogatari (The Tale of Genji), which was written in the Heian period (794-1185). Some believe that tonjiki evolved into a triangular shape so that they would fit better on plates.

First school lunch
School lunches were first implemented to provide food for students from poor families in Yamagata prefecture, and of course they featured the staple onigiri.

First onigiri specialist in Tokyo
The oldest onigiri specialist in Tokyo is Onigiri Asakusa Yadoroku, founded just behind Sensoji Temple in 1954. Try out their lunch sets which include tofu miso soup and two onigiris – choose from a range of ingredients including takuan (pickled radish), tarako (salted fish roe), salmon, shirasu (whitebait), okaka (dried bonito flakes), ume (pickled plum) and many more.

New to Japan? The first time you buy an onigiri from the convenience store, you’ll likely end up pulling the whole thing apart as you try to open it because the rice is separated from the seaweed with a thin sheet of plastic to prevent it from getting soggy. In fact, it’s really simple to unwrap – just look for the numbers 1, 2, 3 on the packaging:

1. Pull the middle strip down, all the way around to the back.

2. Gently remove the right sleeve. We stress, GENTLY.

3. And then the left sleeve.


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