01 - Rinse sushi rice under cold water until water runs clear. Combine rice and water in a saucepan. Bring to a boil, cover, reduce heat to low, and simmer for 18-20 minutes. Remove from heat and let stand covered for 10 minutes.
02 - Whisk rice vinegar, sugar, and salt in a small bowl until dissolved. Gently fold the seasoning mixture into the cooked rice. Allow rice to cool completely to room temperature.
03 - Combine soy sauce, sesame oil, sriracha, mayonnaise, rice vinegar, honey, minced garlic, and grated ginger in a mixing bowl. Whisk until smooth and well incorporated.
04 - Add diced tuna to the spicy marinade. Gently toss to coat evenly without breaking up the fish. Refrigerate for at least 10 minutes to develop flavors.
05 - Slice avocados, cucumber, carrots, radishes, and scallions into thin, even pieces. Keep ingredients separate until serving for optimal presentation.
06 - Divide cooled seasoned rice among four bowls. Arrange marinated tuna, avocado, cucumber, carrots, radishes, and scallings on top. Garnish with sesame seeds, nori strips, and optional toppings like pickled ginger, furikake, or chili slices. Serve immediately.