In a medium bowl, combine soy sauce, five-spice powder, and 1 tablespoon mirin. Pat the chicken dry with paper towels. Add to the bowl and turn to thoroughly coat. Set aside to marinate, turning occasionally, for at least 20 minutes.

In a separate medium bowl, combine the zucchini, white bottoms of the scallions, cilantro, 1 tablespoon vinegar,1 teaspoon sesame oil, the remaining mirin, and garlic. Drizzle with olive oil and season with salt and pepper. Set aside to marinate, stirring occasionally, for at least 10 minutes. Season with salt and pepper to taste.

In a medium pan, heat 2 teaspoons sesame oil on medium-high until hot. Add the marinated chicken (reserving the marinade) and cook 2 to 3 minutes on the first side, or until browned. Flip and add the reserved marinade, remaining 1 tablespoon vinegar, and ½ cup of water. Cook, frequently spooning the sauce over the chicken, 7 to 8 minutes, or until coated and cooked through. Turn off the heat.

Serve chicken with rice and zucchini salad.