Trim chicken thighs (or other cuts) and cut into 40–50 g bite-sized pieces.
In a bowl, combine grated ginger, grated garlic, tamari (or soy), sake, salt, sugar, and oil. Add chicken and toss until coated.
Marinate for 15–30 minutes in the refrigerator.
Mix potato starch and rice flour in a shallow bowl. Coat chicken pieces lightly in flour mix (1st coat), shake off excess, then rest 5–10 minutes.
Coat again (2nd coat) for extra crispness. Place on a tray in a single layer.
Preheat air fryer to 200 °C / 390 °F. Lightly oil the basket.
Air fry chicken 8–10 minutes, flipping halfway. Rest 2–3 minutes.
Increase heat to 240 °C / 465 °F and air fry another 3 + 2 minutes until golden and crisp.
If your air fryer doesn’t reach 240 °C, extend the cooking time until the chicken is deep golden.
In all cases, cook until the chicken reaches an internal temperature of 165 °F / 74 °C.