Cook the brown rice according to package instructions and allow it to cool to room temperature.
Pat the ahi tuna dry with a paper towel and slice into uniform 1/2-inch cubes.
In a small glass bowl, whisk together the tamari, sesame oil, rice vinegar, grated ginger, minced garlic, and red pepper flakes.
Toss the tuna cubes in the marinade and refrigerate for 10 minutes to allow the flavors to penetrate.
Slice the cucumber into thin rounds, dice the avocado, and ensure the edamame is thawed and shelled.
Divide the cooled brown rice into a serving bowl and top with the marinated tuna.
Arrange the cucumber, edamame, and avocado slices around the tuna for a vibrant presentation.
Finish the bowl with a sprinkle of sliced green onions, sesame seeds, and sea salt before serving.