In a medium bowl, combine the drained canned tuna, mayonnaise, sriracha, soy sauce, and sesame oil. Mix thoroughly until the tuna is fully coated and broken down into smaller flakes.
Divide the cooked white rice evenly between two serving bowls. If using leftover or meal-prepped rice, warm it slightly in the microwave before assembling.
Arrange the sliced avocado and diced cucumber over the rice in each bowl.
Spoon the spicy tuna mixture into the center of each bowl alongside the fresh vegetables.
Garnish generously with sliced green onions and furikake seasoning. Drizzle with additional spicy mayo or sriracha if desired, and serve immediately.