Pat the sashimi-grade ahi tuna dry with a clean paper towel and slice into uniform 1/2-inch cubes.
In a medium glass bowl, whisk together the tamari, toasted sesame oil, rice vinegar, grated fresh ginger, sriracha, and lime juice until well combined.
Add the tuna cubes to the marinade, tossing gently to coat every piece, and let it marinate in the refrigerator for 10 minutes.
While the tuna marinates, thinly slice the cucumber into rounds and the green onions on a bias.
Place the warm cooked jasmine rice in the bottom of a serving bowl and top with the marinated tuna, shelled edamame, cucumber slices, and the avocado quarter.
Drizzle any remaining marinade over the bowl and garnish with the sliced green onions and black sesame seeds.