Place the chicken thighs in a bowl for marinating.
Add soy sauce and mirin and mix well until the chicken is well coated in marinade. Allow it to marinate overnight.
Making Hawaiian Teriyaki Sauce
Combine the Hawaiian Teriyaki Sauce ingredients in a saucepan and simmer for 5-10 minutes until it reduces by about half. It'll slightly thicken in the process. Set aside.
Air Frying the Chicken
Place the chicken thighs skin side up in a single layer in the air fryer. Air fry at 350°F for 10 minutes.
Flip the chicken over and air fry with the skin side down for another 5 minutes or until the internal temperature of the thickest part reads 165°F.
Brush a generous amount of teriyaki sauce on the bottom side of the chicken thighs. Flip the chicken over and baste the skin side as well.
Air fry with the skin side up at 325°F for 3-5 minutes until the sauce begins to thicken and form a coating. Keep a close eye on it and be careful not to let the sauce burn. Pull out the chicken thighs as soon as the sauce is thick and sticky.
Allow it to rest for 5-10 minutes before slicing. Serve with steamed rice.