Start by preparing the rice according to package instructions if it's not already cooked. Allow it to cool slightly before using it in the bowl.
Cut the fresh tuna into small cubes. Place the tuna in a mixing bowl.
In a separate small bowl, combine soy sauce, sesame oil, rice vinegar, and sriracha (if using). Mix well.
Pour the sauce over the cubed tuna and gently toss to coat. Let it marinate for about 5 minutes.
In two serving bowls, divide the cooked rice evenly as the base.
Top the rice with the marinated tuna, sliced avocado, cucumber, shredded carrots, and edamame.
Drizzle any remaining sauce over the topped bowls.
Garnish with sesame seeds and fresh cilantro or green onions.