01 - Place sushi rice in a fine-mesh strainer and rinse under cold running water, gently agitating with your hand, until the water runs completely clear. Drain thoroughly.
02 - Transfer the rinsed rice and 2 cups of water to a medium saucepan. Bring to a rolling boil over medium-high heat, then cover tightly with a lid, reduce heat to low, and simmer for 15 minutes. Remove the pan from heat and let it rest, still covered, for 10 minutes to allow the steam to finish cooking the grains.
03 - While the rice rests, whisk together rice vinegar, sugar, and salt in a small bowl until fully dissolved. Transfer the warm rice to a large mixing bowl, pour the vinegar mixture over it, and gently fold with a rice paddle using a slicing motion. Fan the rice briefly to cool it slightly and achieve a glossy finish.
04 - Shred the imitation crab sticks into thin strands. Dice the avocado into bite-sized cubes. Julienne the cucumber into matchstick strips. Cut the nori sheets into thin strips. Thinly slice the green onion on a bias. Chop the pickled ginger into small pieces.
05 - In a small bowl, combine mayonnaise with sriracha and stir until smooth and evenly blended. Adjust the sriracha amount to taste.
06 - Divide the seasoned rice evenly among four serving bowls. Arrange the shredded crab, diced avocado, julienned cucumber, nori strips, and pickled ginger in neat sections over each bed of rice.
07 - Drizzle each bowl with spicy mayo and soy sauce. Sprinkle generously with toasted sesame seeds and sliced green onions. Serve immediately with additional soy sauce on the side.