Halloween Spicy Tuna Onigiri (Japanese Rice Balls)

These Spicy Tuna Onigiri are my Halloween-inspired twist on a classic Japanese comfort food. But obviously they taste delicious any time of year!

Onigiri, or Japanese rice balls, are simple yet deeply nostalgic. You’ll find them everywhere in Japan, from convenience stores to homemade bento boxes. Traditionally, they’re filled with salty or savory ingredients like pickled plum, salmon, or kombu, then wrapped in nori (seaweed).

My version keeps that comforting, grab-and-go spirit but adds a spicy, creamy tuna filling that’s as addictive as it is easy to make.

The filling comes together with canned tuna, a spoonful of gochujang for heat, and creamy Kewpie mayo to balance everything out. The gochujang adds a subtle smokiness and depth, while sesame seeds bring a nutty crunch that ties the flavors together.

Once stuffed inside warm, seasoned rice and wrapped in seaweed, you get that perfect balance of soft, spicy, and slightly crisp with every bite. Also, feel free to omit the seaweed if you’re not into it!

I especially love making these in October because their dark nori wrapping gives them such a fun, Halloween-ready look. Jeff said he thinks they look like little bats!

But honestly, these Spicy Tuna Onigiri are too good to save just for spooky season. They make an amazing lunch, snack, or quick dinner any time of year, and they’re portable enough for picnics, meal prep, or road trips.

So how do you make them? Let’s dive into it!

What is Onigiri?

Onigiri, also known as Japanese rice balls, are a staple of Japanese home cooking and convenience store culture. They’re made by shaping warm rice – usually seasoned with salt – into a triangle, ball, or cylinder, often with a savory filling tucked inside.

Common fillings include salted salmon, pickled plum (umeboshi), or tuna mayo, though there are endless variations depending on region and taste.

Wrapped in a sheet of nori (seaweed) for easy handling, onigiri are the ultimate portable snack. Simple, comforting, and satisfying. They’re a symbol of care in Japanese culture, often found in homemade bento lunches or given to loved ones as an easy, heartfelt meal. Despite their simplicity, onigiri carry a lot of warmth and nostalgia, embodying the beauty of everyday Japanese food.

Growing up, my mom would pack us onigiri all the time whether it was for school, a roadtrip, or a picnic.

Click the rice cooker photos to see my favorite rice cookers. I included a budget-friendly rice cooker I love! I use the Tiger 5.5-cup model shown. About 1/2 cup of Japanese short- or medium-grain rice makes 1 serving.

Key Features to Look For in a Rice Cooker:

• Timer and Keep Warm Function: Useful for planning meals ahead of time and keeping them warm until you’re ready to eat.
• Steaming Basket or Tray: Allows you to steam vegetables or cook other ingredients while the rice cooks.
• Multiple Cooking Functions: Ensure it has settings for steaming, slow cooking, and possibly even baking.
• Non-Stick Inner Pot: Makes cleaning easier and prevents sticking.

How Long Does Onigiri Stay Good For?

Onigiri is best enjoyed fresh, but how long it stays good depends on how it’s stored:

• At room temperature: If you plan to eat it the same day, it can sit out for about 4-6 hours as long as it’s in a cool, dry place. Many people wrap it in plastic wrap or store it in a sealed container to keep the rice from drying out.
• In the fridge: Onigiri can last up to 2-3 days, but the rice will firm up and lose its soft texture. To revive it, lightly microwave it for 15-20 seconds with a damp paper towel on top before eating.
• In the freezer: You can freeze onigiri (without the seaweed) for up to 1 month. Wrap each rice ball tightly in plastic wrap and place them in a freezer bag. When ready to eat, reheat in the microwave until warm and wrap with fresh nori before serving.

For the best texture and flavor, though, onigiri is always at its peak the day it’s made.

Ingredients:

• White Rice: The base of onigiri. Soft, slightly sticky short-grain rice that holds its shape perfectly when molded.
• Kewpie Mayo: A Japanese-style mayonnaise that’s creamier and richer than regular mayo, adding smoothness and umami to the filling.
• Canned Tuna: A convenient and protein-packed filling that pairs beautifully with the creamy mayo and spicy gochujang. I love using Korean canned tuna, but anything works great!
• Gochujang: A Korean fermented chili paste that brings a deep, savory heat and a hint of sweetness to the mix. I’ll touch on this more below.
• Roasted Sesame Seeds: Add a nutty aroma and delicate crunch, tying all the flavors together and enhancing the overall texture.
• Seaweed (Nori): Provides that signature salty, slightly crisp outer layer. Feel free to omit it if you don’t like seaweed!

The Best Tuna to Use

I like using Korean canned tuna for this recipe because it’s often packed in oil and lightly seasoned, which gives the filling extra richness and flavor. It blends especially well with gochujang and Kewpie mayo! Together, it creates a perfectly balanced spicy and savory bite.

Korean canned tuna is often seasoned and packed with flavor right out of the can. Unlike most Western canned tuna, which is typically plain and packed in water or oil, Korean varieties often come infused with ingredients like soy sauce, chili, sesame oil, or even vegetables such as onions and peppers. This gives them a richer, more savory taste and a softer, more flavorful texture. It’s especially popular for mixing into rice dishes, stews, or spicy sauces.

That said, any type of canned tuna works great. So use whatever you have on hand or prefer. The seasonings do all the heavy lifting, so you’ll still end up with delicious, flavorful onigiri.

What is Gochujang?

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