Cube the sushi-grade ahi tuna into bite-sized 1/2-inch pieces and place them in a medium glass bowl.
In a small jar, whisk together the coconut aminos, toasted sesame oil, grated ginger, and minced garlic until well combined.
Pour the marinade over the tuna, tossing gently to coat, and let it marinate in the refrigerator for 15 minutes to develop flavor.
In a separate bowl, toss the diced mango with lime juice and chopped cilantro to create a bright, tropical salsa.
Divide the cooked brown rice into serving bowls and top with the marinated tuna, sliced cucumber, shelled edamame, and avocado.
Sprinkle the finished bowls with black sesame seeds, sea salt, and black pepper before serving immediately.