Classic Japanese Onigiri with Tuna

If you’ve ever tried to explain onigiri to a kid who’s never had one, just call it what it is: a sushi sandwich you eat with your hands, no chopsticks required. My kids were sold before I even finished the sentence. This tuna mayo version is the most popular onigiri flavour in all of Japan: a creamy, savoury tuna filling made with Kewpie mayo, tucked into rice and wrapped in nori. It’s lunchbox gold, it takes under 35 minutes, and the filling is totally customizable. Keep it simple for the picky eaters, add scallions or a little hot sauce for the adventurous ones, or go full chaos with a tiny dab of wasabi if your kids’ palates are ready for a challenge.

What is Onigiri?

Onigiri (おにぎり) are one of Japan’s oldest comfort foods, eaten for over a thousand years as portable fuel for everything from samurai to schoolchildren. The name comes from the Japanese verb nigiru, to grip or squeeze, which is exactly how they’re shaped. Today, they’re a staple of Japanese convenience stores, bento boxes and home kitchens, with tuna mayo being the runaway most popular filling since 7-Eleven Japan introduced it in the 1980s.

The Secret to Perfect Onigiri

• Use Japanese short-grain rice only: it’s the sticky factor that holds everything together
• Keep your rice warm: cold rice won’t bond, and your onigiri will crumble
• Wet hands + sea salt before every single rice ball: prevents sticking AND seasons the outside at the same time
• Drain your tuna really well: excess moisture = soggy onigiri
• Don’t overfill: the filling should be no more than 1/5 of the total volume
• Press and turn gently: 3 to 5 light rotations are all you need; overworking kills the texture
• Add the nori just before serving if possible: keeps it crispy instead of soggy

Two Ways to Shape Them

In this recipe, I’m showing you two ways to make them.

The first is by hand, the traditional Japanese way; once you get the hang of it, it’s deeply satisfying. The trick is warm rice, cold wet hands rubbed with sea salt, and a light press-and-turn motion, no overworking, just a few gentle rotations, and you’ve got a perfect triangle. The less you handle the rice, the better the texture.

The second method is using an onigiri mould, which is an absolute game-changer for lunchbox production days and genuinely one of the best ways to get kids involved in the kitchen: fill, press, pop out, repeat. They will do this for an alarming amount of time.

What is Kewpie Mayo?

You know that creamy sauce drizzled over sushi rolls and Japanese street food that you can never quite put your finger on? That’s Kewpie. Japan’s iconic mayonnaise has been made since 1925; it’s made with egg yolks only rather than whole eggs, seasoned with rice vinegar and a touch of MSG, giving it a richer, thicker texture and a certain je ne sais quoi that regular mayo simply doesn’t have. You can find it in most Asian grocery stores or online, and once it’s in your fridge, you will find excuses to put it on everything.