For the sushi rice: In a large mixing bowl, rinse the rice by covering with cold water and straining. Repeat until the water runs clear, three times. Using a rice cooker on the highest setting or a medium saucepan over high heat, bring 2 cups plus 2 tablespoons water and the sushi rice to a boil. Reduce the heat to low. Cover and simmer for 15 minutes. Being careful not to disturb, turn off the heat and allow the rice to stand, covered, for an additional 15 minutes.
For the sushi zu: Combine the sugar, vinegar and salt in a small saucepot. Heat just until dissolved.
Remove the rice from the cooker or saucepan to a large glass or wooden bowl with a wooden paddle. Gently fold in the sushi zu. Bring the rice to room temperature and allow to rest for at least 1 hour covered with a towel.
For the spicy tuna: Combine the Sriracha, mayo, sambal and sesame oil in a medium glass bowl with a whisk. Once incorporated, fold in the tuna and scallions. Mix thoroughly. Add in the chili powder, hot sesame oil and sprinkle with salt and pepper. Cover and refrigerate until ready for use.
For the vinaigrette: Whisk together the mustard, yuzu juice, wasabi, lemon zest and lime zest. Slowly drizzle in the oil, whisking to emulsify. Fold in the jalapeno. Season with salt and pepper. Reserve until ready for use.
Form the sushi rice into nigiri patties, 2 tablespoons each. Bring the oil to 375 degrees F in large cast-iron or heavy-gauge pot over medium-high heat. Fry the tots until browned on all sides, crispy on the outside and soft in the middle, 8 to 10 minutes. Remove from the oil and place on a towel-lined dish. Loosely cover to keep warm.
To serve: Drizzle the serving plate with unagi sauce. Place the fried nigiri tots on the plate, evenly spaced. Top each patty with 1 tablespoon spicy tuna salad. Garnish with a drizzle of yuzu vinaigrette.
Consumption of raw or undercooked eggs, shellfish and meat may increase the risk of foodborne illness.