In a medium bowl, combine soy sauce, sake, grated ginger, and minced garlic. Add the chicken pieces and marinate for at least 30 minutes in the refrigerator.
In a separate bowl, mix cornstarch, black pepper, and salt. Remove the chicken from the marinade and coat each piece in the cornstarch mixture, shaking off any excess.
Preheat the air fryer to 400°F. Lightly spray the air fryer basket with vegetable oil.
Place the coated chicken pieces in a single layer in the air fryer basket. Spray the tops lightly with vegetable oil. Cook for 10-12 minutes, shaking the basket halfway through, until the chicken is golden brown and crispy.
While the chicken is cooking, prepare the miso glaze by whisking together miso paste, honey, rice vinegar, and sesame oil in a small bowl until smooth.
Once the chicken is done, drizzle the miso glaze over the crispy chicken and toss to coat.
To serve, place a scoop of cooked rice in a bowl, top with the glazed chicken, and garnish with sliced green onions and sesame seeds.