Pat drumsticks very dry with paper towels (this is the crispiness lever). In a bowl, toss drumsticks with oil, salt, pepper, and garlic powder. For extra crisp skin, sprinkle in baking powder and toss again.

Preheat air fryer to 375°F for 3–5 minutes. Place drumsticks in a single layer (work in batches if needed). Air fry 25–30 minutes, flipping at 12–15 minutes, until deeply browned and the thickest drumstick hits 175°F–185°F.

In a small saucepan, add soy sauce, honey, brown sugar, mirin, vinegar, sesame oil, garlic, ginger, water. Bring to a boil, then reduce to a steady simmer for 3–4 minutes. Mix cornstarch and water to make a slurry. Whisk it into the simmering sauce. Simmer 1–3 minutes until thick, glossy, and it coats the back of a spoon. Remove from heat.

Toss cooked drumsticks in a large bowl with half to two-thirds of the glaze (start light; add more as needed). Return glazed drumsticks to the air fryer at 400°F for 2–3 minutes to caramelize and set the glaze. Top with sesame seeds, green onions, and optional gochugaru or chili flakes.