Prepare the brown rice according to package instructions and allow it to cool slightly to room temperature.
Using a sharp knife, cut the sushi-grade ahi tuna into uniform half-inch cubes.
In a small glass bowl, whisk together the tamari, sesame oil, rice vinegar, and grated fresh ginger.
Toss the tuna cubes in the marinade and let them sit in the refrigerator for 10 minutes to absorb the flavors.
Thinly slice the cucumber, radish, and green onion, and slice the avocado into thin wedges.
Place the cooked brown rice in the center of a bowl and arrange the marinated tuna, edamame, cucumber, radish, and avocado around it.
Garnish the bowl with toasted sesame seeds and sliced green onions before serving immediately.