Preheat air fryer to 400°F for 3 minutes while you pat salmon fillets very dry and brush skin lightly with neutral oil.
Mix soy sauce, mirin, brown sugar, rice vinegar, grated ginger, and minced garlic in a small saucepan and simmer over medium heat 2–3 minutes until sugar dissolves.
Stir cornstarch slurry into the glaze, simmer 30–60 seconds until slightly thickened, then remove from heat and stir in sesame oil; reserve 2 tablespoon glaze for serving.
Place fillets skin-side down in a single layer in the air fryer basket and cook at 400°F for 6–7 minutes for 1-inch-thick fillets; thicker fillets may need 8–10 minutes.
Brush each fillet with a thin layer of glaze, then air fry 60–90 seconds more at 400°F until glaze is glossy and edges show light caramelization; remove when internal temp reaches 145°F or flesh flakes easily.
Rest fillets 2–3 minutes, garnish with sliced scallions and toasted sesame seeds, and serve with reserved warm glaze and lemon wedges.