Pat the ahi tuna dry and cut into 1/2-inch cubes.
In a small bowl, whisk together tamari, sesame oil, rice vinegar, grated ginger, and minced garlic.
Toss the tuna cubes in the marinade and let sit in the refrigerator for 10 minutes.
Prepare the tropical salsa by combining diced mango, minced red onion, chopped cilantro, and lime juice in a separate bowl.
Season the salsa with a pinch of sea salt and black pepper.
Place the cooked brown rice in the center of a serving bowl.
Arrange the marinated tuna, mango salsa, sliced cucumber, shelled edamame, and diced avocado over the rice.
Garnish with additional cilantro if desired and serve immediately while cold.