Prep the beef: For easier slicing, place the steak in the freezer for 20–30 minutes until firm but not frozen. Slice against the grain into very thin strips, about 1/8 inch.
Make the marinade: In a large bowl, combine grated pear, soy sauce, brown sugar, sesame oil, garlic, ginger, green onions, mirin or rice vinegar (if using), black pepper, and gochujang or red pepper flakes (if using). Stir until the sugar dissolves.
Marinate: Add the sliced beef to the bowl and toss to coat every piece.
Cover and refrigerate at least 30 minutes, ideally 2–4 hours. For the best flavor, marinate overnight.
Preheat the air fryer: Heat to 390°F (200°C) for 3–5 minutes. Lightly brush or spray the basket with neutral oil to prevent sticking.
Load the basket: Arrange the beef slices in a single layer with minimal overlap.
Work in batches. Shake off excess marinade so it doesn’t pool.
Air fry: Cook for 5–7 minutes, flipping or shaking halfway through. Thin cuts cook fast.
Look for browned edges and just-cooked centers.
Repeat: Transfer cooked bulgogi to a plate and cover loosely to keep warm. Continue with remaining beef.
Garnish and serve: Sprinkle with sesame seeds and extra green onions. Serve over rice with kimchi, sliced cucumbers, and lettuce leaves for wrapping.