Start by marinating the chicken fillets. In a small bowl, whisk together the soy sauce, sesame oil, rice vinegar, and garlic. Place the chicken fillets in a shallow dish, pour the marinade over, and let them sit for at least 20 minutes.
Heat the vegetable oil in a skillet over medium heat. Cook the chicken fillets for 4–5 minutes per side, or until golden brown and cooked through. Let them rest for a few minutes, then slice thinly.
While the chicken rests, prep your salad base. In a large bowl, combine the napa cabbage, carrots, cucumber, and green onions. Toss lightly.
Add the sliced chicken on top of the veggies. Sprinkle with toasted sesame seeds and fresh cilantro.
Drizzle any extra marinade over the salad or serve with additional soy sauce and rice vinegar on the side if you want more flavor.