Rinse the sushi rice thoroughly under cold water until the water runs clear. Cook the rice according to package directions in a rice cooker or saucepan. Once cooked, let it sit covered for 10 minutes.

In a small bowl, whisk together the rice vinegar, sugar, and salt until dissolved. Transfer the cooked rice to a large, wide bowl. Pour the vinegar mixture over the hot rice and gently fold with a rice paddle or spoon until well combined and the rice has cooled slightly. Set aside.

While the rice is cooking, pat the tuna dry with a paper towel. Cut the tuna into uniform 1/2-inch cubes.

In a medium mixing bowl, combine the Kewpie mayonnaise, Sriracha, soy sauce, and toasted sesame oil. Whisk until smooth. Add the cubed tuna and 2 tablespoons of thinly sliced green onions to the sauce. Gently fold until the tuna is evenly coated.

Divide the prepared sushi rice evenly between two serving bowls. Arrange the spicy tuna mix on one side of each bowl. Artfully arrange the diced avocado, sliced cucumber, and cooked edamame around the tuna. Garnish with nori strips, black and/or white sesame seeds, and the remaining sliced green onions.

Serve immediately with optional sides like pickled ginger, a dab of wasabi, or an extra drizzle of Sriracha for an added kick.