In a bowl, whisk together the soy sauce, honey, rice vinegar, sesame oil, minced garlic, and grated ginger. This will be your marinade.
Place the chicken thighs in a resealable plastic bag or a shallow dish and pour the marinade over them. Ensure the chicken is well coated. Seal the bag or cover the dish and marinate in the refrigerator for at least 30 minutes, or up to 2 hours for more flavor.
After marinating, remove the chicken thighs from the marinade and shake off excess liquid. Reserve the marinade for later.
Preheat your air fryer to 375°F (190°C).
Place the chicken thighs skin-side down in the air fryer basket. Cook for 10 minutes.
While the chicken is cooking, take the reserved marinade and pour it into a small saucepan. Bring it to a gentle boil and then reduce heat, allowing it to simmer for 5 minutes. Mix cornstarch and water together and stir into the simmering marinade to thicken it slightly. Remove from heat once thickened.
After 10 minutes, flip the chicken thighs and brush them with some of the thickened marinade. Cook for an additional 10-12 minutes, or until the internal temperature reaches 165°F (75°C) and the skin is crispy.
Once done, remove the chicken thighs from the air fryer and let them rest for 5 minutes.
Serve the chicken thighs drizzled with the remaining thickened marinade, and garnish with sesame seeds and sliced green onions.