In a large bowl, combine soy sauce, dark soy sauce, five-spice powder, white pepper, sugar, and minced garlic. Mix well until the sugar dissolves, creating a fragrant marinade. Add the boneless chicken thighs, ensuring they are well-coated. Cover and let marinate for at least 30 minutes, preferably overnight.

Preheat your air fryer to 380°F. Take the marinated chicken out of the fridge and arrange the thighs skin-side up in the air fryer basket.

Cook the chicken thighs at 380°F for 15 minutes, monitoring closely for a golden-brown appearance.

After 15 minutes, check the internal temperature with a meat thermometer; it should read at least 165°F. If not, continue air frying in 2-minute increments.

Remove the chicken from the air fryer and let it rest for about 5 minutes before serving.