Prep the beef: Pat the steak dry.
Slice into long, even strips against the grain, about 1/4–1/2 inch thick. This keeps the meat tender and helps it cook evenly in the air fryer.
Make the marinade: In a bowl, whisk soy sauce, brown sugar, mirin, honey, garlic, ginger, and sesame oil. Reserve 1/4 cup of this mixture in a small saucepan for glazing later.
Marinate: Add the beef strips to the remaining marinade, toss to coat, and cover.
Marinate at least 30 minutes in the fridge, or up to 8 hours for deeper flavor.
Soak the skewers: If using bamboo skewers, soak them in water for 20–30 minutes to prevent burning.
Thread the skewers: Thread the marinated beef onto skewers, weaving each strip back and forth for even cooking. If adding peppers, onions, or pineapple, alternate them with the beef. Let excess marinade drip off.
Preheat the air fryer: Set to 400°F (200°C) for 3–5 minutes.
Lightly oil the air fryer basket or use a liner designed for air fryers.
Cook the skewers: Arrange in a single layer with space between them. Air fry for 8–10 minutes, flipping halfway through. Cook until edges are caramelized and internal temp reaches about 135–140°F for medium.
Thicken the glaze (optional but great): Bring the reserved marinade to a simmer in the small saucepan.
Stir in the cornstarch slurry and cook 1–2 minutes, until glossy and thick. If too thick, add a splash of water.
Glaze and garnish: Brush the cooked skewers with the thickened teriyaki sauce. Sprinkle with sesame seeds and green onions.
Serve: Plate over steamed rice or noodles with extra sauce on the side.
Add a crisp cucumber salad or steamed broccoli for balance.