Mix bite sized chicken thigh pieces with ground ginger, garlic, sugar, mirin and sake in a bowl. Cover & marinate for 4 hours or overnight.
Place potato flour onto a large plate. Take the chicken out of the marinade and dredge it in the flour, one piece at a time.
Shake any excess flour from the chicken and place in the air fryer basket / tray in a single layer.
Spray the chicken with oil and cook on 200C / 380F for 12 minutes, flipping the chicken pieces halfway, or until golden and crisp.