Gather the ingredients. Start by washing the 1 cup short-grain rice in cold water to remove the starch then cook it in the rice cooker. The rice should be done by the time you are finished with the spicy tuna mix.
Clean and chop 3 green onions or scallions.
The Spicy Tuna
To make the spicy tuna salad, drain the can of 142 g Ahi tuna in olive oil then transfer to a bowl and break up the tuna chunks into small flakes using a fork. Add 2 Tbsp. Japanese Kewpie mayonnaise, 2 Tbsp. Sriracha and ½ tsp. soy sauce. Mix well to combine. If you do like too spicy, decrease the Sriracha.
Add the chopped 3 green onions or scallions, ½ tsp. lemon juice and 2 Tbsp. roasted black sesame seeds mix well.
The Onigiri
Prepare the onigiri rice by mixing 1 Tbsp. roasted black sesame seeds into the slightly cooled rice.
Cut the 2 Nori sheets into 3 pieces each. Make sure to have the glossy and smooth side on the table.
Wet the onigiri mold with hot water and fill with rice using a spoon. Proceed to add the tuna filling to the center.
Top with more rice and compressing firmly. Release the formed rice ball onto a plate or cutting board.
Place the onigiri in the middle of your strip of nori. Proceed to wrap each onigiri and tuck the nori under the bottom (like a bathrobe). Place a spoon of tuna mayo filling on the top. Proceed to complete the rest of the onigiris.
The Serving
Serve immediately for crispy texture. They should be eaten during the same day as the rice will harden if left in the fridge. Enjoy your fresh Spicy Tuna Onigiri [ピリ辛マグロおにぎり].