Cook the brown rice according to package instructions and set aside to cool slightly.
Slice the sushi-grade ahi tuna into bite-sized 1/2-inch cubes.
In a small glass bowl, whisk together the tamari, sesame oil, lime juice, grated ginger, and sriracha to create the marinade.
Toss the tuna cubes gently in the marinade and let sit for 5 minutes while you prepare the vegetables.
Thinly slice the cucumber, radishes, and green onion, and pit the avocado to slice into wedges.
Assemble the bowl by placing the rice at the base, then topping with the marinated tuna, edamame, cucumber, radishes, and avocado.
Garnish with sesame seeds and sliced green onions before serving.