Cook the white rice according to package instructions and set aside to cool slightly.
Slice the sushi-grade ahi tuna into bite-sized half-inch cubes using a sharp knife.
In a small bowl, whisk together the tamari, toasted sesame oil, rice vinegar, and grated fresh ginger.
Gently toss the tuna cubes in the marinade until evenly coated and let sit for 5 minutes.
Thinly slice the cucumber, radishes, green onion, and avocado.
Build the bowl by placing the rice at the bottom and topping it with the marinated tuna, edamame, and prepared vegetables.
Garnish with sesame seeds and sliced green onions before serving.