Begin by rinsing your sushi rice under cold water until the water runs clear; this usually takes about 3-4 rinses.

Cook the rice according to the package instructions, typically in a rice cooker or a pot with a lid, adding the appropriate amount of water, and allow it to steam for 18-20 minutes until fluffy and tender.

In a small saucepan, combine rice vinegar, granulated sugar, and kosher salt. Heat over low heat, stirring gently until the sugar and salt dissolve completely.

Once your sushi rice is done cooking, transfer it to a large bowl and gently fold in the prepared sushi vinegar while it's still warm.

Line a square or rectangular dish with plastic wrap and press the sushi rice into an even layer about 1-inch thick. Cover the top with additional plastic wrap and refrigerate for at least 3 hours.

While the rice is chilling, finely dice the sushi-grade Ahi tuna into small cubes, ensuring a clean and fresh cut. Combine the chopped tuna with sliced scallions in a bowl.

In a separate bowl, whisk together Kewpie mayonnaise, Sriracha, and ponzu sauce until smooth and well combined.

Once your rice has chilled, remove it from the refrigerator and cut it into rectangles or squares, about 2 inches in size.

Heat a generous amount of neutral oil in a deep skillet over medium-high heat until shimmering. Fry the rice pieces for about 2-3 minutes on each side, or until golden brown and crispy.

Top each crispy rice bite with a spoonful of the spicy tuna mixture, sprinkle black sesame seeds on top, and finish off with a slice of fresh jalapeño.