Spicy Tuna Onigiri Delight

Featured in: Everyday Flavors

This dish features tender Japanese short-grain rice, gently seasoned and shaped into bite-sized triangles filled with a creamy, spicy tuna blend. Wrapped neatly with nori, these rice balls combine savory, tangy, and mildly spicy notes for a balanced and portable treat. Preparation includes cooking sushi-style rice, blending fresh tuna with mayo, Sriracha, and sesame oil, then assembling the components into perfectly shaped onigiri. Ideal for an easy lunch or snack, they offer both convenience and bold flavor in every bite.

Updated on Sun, 15 Feb 2026 09:45:00 GMT
Spicy tuna onigiri rice balls filled with flavorful tuna mixture and wrapped in crisp nori seaweed.  Save
Spicy tuna onigiri rice balls filled with flavorful tuna mixture and wrapped in crisp nori seaweed. | oventhyme.com

My coworker Sarah once brought these to a team lunch, and I watched everyone's faces light up the moment they unwrapped the nori—there's something about a perfectly formed triangle of rice that just feels like care in edible form. She'd learned to make them during a semester abroad in Tokyo, and when she finally taught me her method, I realized the magic wasn't in fancy technique but in understanding how the rice needs to cool, how the filling should peek through just right, and why damp hands make all the difference. Now I make them constantly, sometimes for road trips, sometimes just because I want something that tastes fresh and intentional.

I remember bringing these to a picnic last summer and realizing halfway through that they'd somehow become the thing people reached for first, even before the fancy sandwiches someone else had spent hours on. There's a confidence that comes with knowing you've made something portable and delicious, something that holds together in your hands and tastes better with every bite.

Ingredients

  • Japanese short-grain rice (2 cups): This is the backbone of everything—short-grain rice has the right starch content to stick together without being mushy, which is exactly what you need for shaping.
  • Water (2 1/4 cups): The ratio matters more than you'd think; too much and your rice gets soggy, too little and it's crunchy.
  • Rice vinegar (1 tablespoon): This gives the rice that subtle tang that makes you taste something bright even though you can't quite name it.
  • Sugar and salt (1 teaspoon and 1/2 teaspoon): Together they balance the vinegar and bring out the rice's natural sweetness.
  • Canned or sushi-grade tuna (5 oz / 140 g): Canned is convenient and reliable; sushi-grade raw tuna is more authentic but requires confidence in your fishmonger.
  • Kewpie mayonnaise (2 tablespoons): Japanese mayo has a richer, almost buttery quality that makes the filling creamy without being heavy—regular mayo works but tastes different.
  • Sriracha (1 teaspoon): Start with less and add more; heat builds as it sits, and everyone's tolerance is different.
  • Soy sauce and sesame oil (1 teaspoon each): These create the umami backbone that makes your mouth think this is restaurant-quality tuna.
  • Green onion (1 chopped): The fresh bite cuts through the richness and adds a subtle sharpness that wakes up the whole filling.
  • Nori sheets (3 halved): Buy the good stuff if you can—cheaper seaweed tastes papery and ruins the whole experience.
  • Toasted sesame seeds (optional): These add a nutty crunch that transforms a good onigiri into something you'll think about later.

Instructions

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Rinse and cook your rice:
Cold water and your hands work better than anything else for rinsing—you're looking for water that runs clear, which usually takes three or four rounds. Once it's cooked and has rested those ten minutes, it'll have the right texture to work with, neither too hot nor too cool.
Season the warm rice:
Fold gently so you're coating each grain without squashing it into paste; this is where patience actually changes the texture. The rice should smell faintly of vinegar and taste subtly sweet, nothing aggressive.
Mix your spicy tuna filling:
Combine everything in one bowl and taste as you go—if it's not spicy enough now, you're probably going to want more Sriracha. The mixture should smell fragrant and slightly fishy, with mayo visible throughout.
Prepare for shaping:
Wet hands prevent sticking better than any other trick, and that light salt gives you grip without making things taste oversalted. Think of your palm as a mold, not a weapon—gentle pressure does the job.
Shape the onigiri:
Flatten rice in your palm, add filling to the center, fold carefully, and press until it holds but doesn't feel rock-hard. A triangle is traditional but honestly, any neat shape works if it feels solid enough to not fall apart when you pick it up.
Wrap with nori:
A strip around the base looks polished and gives you something to grab without touching rice. The nori will soften slightly from the rice's moisture, which is exactly what you want.
Finish and store:
Sesame seeds add texture if you're serving right away; they get soft if they sit too long. Plastic wrap keeps them fresh for hours if you need to pack them for later.
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Japanese spicy tuna onigiri with seasoned rice, creamy tuna filling, and toasted sesame seeds for crunch.  Save
Japanese spicy tuna onigiri with seasoned rice, creamy tuna filling, and toasted sesame seeds for crunch. | oventhyme.com

There's a moment when you hold a freshly shaped onigiri in your hand and it's still warm, the nori still crisp, and you realize you've made something that's both simple and somehow perfect. That's the moment I understood why onigiri matter in Japanese cuisine—they're not complicated, but they're made with intention.

Why Temperature and Timing Matter

Hot rice burns your hands and makes the filling ingredients wilt; cold rice doesn't hold together the way warm rice does, but there's a sweet spot right around room temperature where everything cooperates. The first time I shaped these when the rice was still steaming, I wasted half a batch and learned that patience at this stage saves frustration later.

Choosing Your Tuna

Canned tuna in water is reliable and convenient—just make sure you drain it well or your filling becomes watery. If you want to use raw, sushi-grade tuna, dice it finely and know that this version tastes lighter, more delicate, and slightly more special, though it demands a bit more confidence in your ingredients.

Storage and Serving Suggestions

These are best served fresh, but they keep wrapped in plastic for several hours without getting soggy, which makes them perfect for lunches that need to travel. A little miso soup or a cucumber salad on the side elevates the whole meal into something that feels thoughtfully put together.

  • Wrap them individually in plastic wrap if you're packing them for lunch the next day.
  • Let them sit at room temperature for a few minutes before eating if they've been in the fridge—cold rice tastes heavier.
  • If the nori gets soft, that's actually fine; it means the rice is at the right moisture level.
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Hand-shaped onigiri rice balls featuring spicy tuna filling, nori wrap, and vibrant green onion garnish. Save
Hand-shaped onigiri rice balls featuring spicy tuna filling, nori wrap, and vibrant green onion garnish. | oventhyme.com

Make these once and you'll understand why they've been lunch in Japan for centuries—they're proof that the best food doesn't have to be complicated. Once you've shaped a few, it becomes second nature, and then you're free to just enjoy making something good.

Kitchen Guide

What type of rice is best for onigiri?

Japanese short-grain rice works best due to its sticky texture, which helps the rice hold shape when molded.

Can I substitute the spicy tuna filling with cooked tuna?

Yes, canned tuna can be used as long as it is well drained and mixed with the seasonings to ensure flavorful filling.

How do I prevent the rice from sticking to my hands when shaping onigiri?

Wet your hands with water and lightly sprinkle with salt before shaping to keep rice from sticking and add subtle seasoning.

What is the purpose of wrapping onigiri with nori?

Nori adds a savory, slightly crisp contrast and helps keep the rice balls intact while providing additional umami flavor.

Can I adjust the spiciness of the tuna filling?

Yes, simply reduce or omit the Sriracha or hot sauce to control the heat level according to preference.

Spicy Tuna Onigiri Delight

Delicious seasoned rice balls with a spicy tuna center wrapped in nori for an easy handheld snack.

Prep duration
20 min
Kitchen time
20 min
Complete duration
40 min
Created by Grace Mitchell


Skill level Easy

Heritage Japanese

Output 6 Portions

Dietary requirements None specified

What you'll need

Rice Base

01 2 cups Japanese short-grain rice
02 2 1/4 cups water
03 1 tablespoon rice vinegar
04 1 teaspoon sugar
05 1/2 teaspoon salt

Spicy Tuna Filling

01 1 can (5 oz) tuna in water, drained
02 2 tablespoons mayonnaise
03 1 teaspoon Sriracha
04 1 teaspoon soy sauce
05 1 teaspoon sesame oil
06 1 green onion, finely chopped

Assembly

01 3 sheets nori (dried seaweed), cut in half
02 Salt for shaping
03 Toasted sesame seeds (optional)

Method

Phase 01

Prepare the Rice: Rinse rice under cold water until water runs clear. Combine rice and water in a pot or rice cooker and cook according to package instructions. Let rest for 10 minutes after cooking.

Phase 02

Season the Rice: In a small bowl, mix rice vinegar, sugar, and salt until dissolved. Gently fold into warm rice and allow to cool to room temperature.

Phase 03

Make the Spicy Tuna Mixture: In a bowl, combine drained tuna, mayonnaise, Sriracha, soy sauce, sesame oil, and chopped green onion. Mix thoroughly and adjust spice level to taste.

Phase 04

Prepare Shaping Station: Fill one bowl with water and place salt in another small bowl. Wet your hands and sprinkle lightly with salt in preparation for shaping.

Phase 05

Form the Onigiri: Take approximately 1/2 cup of cooled rice and flatten gently in your palm. Place 1 to 2 teaspoons of spicy tuna filling in the center. Fold rice around filling and shape into a triangle, pressing gently but firmly to secure.

Phase 06

Wrap with Nori: Wrap a strip of nori around the bottom of each onigiri. Sprinkle with toasted sesame seeds if desired.

Phase 07

Serve: Serve immediately or wrap tightly in plastic wrap for storage and later consumption.

Kitchen tools needed

  • Rice cooker or pot with lid
  • Sharp knife
  • Mixing bowls
  • Spoon or rice paddle
  • Plastic wrap for optional storage

Allergy notes

Always review ingredients for potential allergens and seek professional medical advice when uncertain.
  • Contains fish (tuna)
  • Contains egg (mayonnaise)
  • Contains soy (soy sauce and mayonnaise)
  • Contains sesame (oil and optional seeds)
  • Contains gluten in soy sauce unless gluten-free alternative used
  • May contain traces of shellfish depending on nori and mayonnaise brands

Nutrition breakdown (per portion)

Values shown are estimates only - consult healthcare providers for specific advice.
  • Energy: 185
  • Fats: 5 g
  • Carbohydrates: 28 g
  • Proteins: 7 g