Place the chicken pieces in a large bowl, pour the teriyaki sauce over the chicken, and toss to coat well. Marinate for 2 hours at room temperature or overnight in the refrigerator.
Remove the chicken from the marinade and drain on paper towels, blotting any excess moisture.
Dust the chicken pieces lightly with the cornstarch; do not coat them. Salt and pepper the chicken pieces.
Heat the oil in a large nonstick skillet over medium heat until hot, but not smoking. Reduce the heat slightly and add as many chicken pieces as will fit without crowding. Fry 6 to 7 minutes per side until golden brown and cooked through. Repeat with the remaining chicken. Serve hot.