Combine soy sauce, brown sugar, pineapple juice, sake, rice vinegar, garlic, ginger, monosodium glutamate, red chilli flakes and sesame seeds in a small saucepan. Bring to a simmer; cook for 10 minutes. Remove sauce from heat and let cool.
Cut wings at the joint to make drumettes. Transfer to a large resealable plastic bag. Pour in sauce. Marinade in the refrigerator, at least 3 hours and up to overnight.
Preheat barbecue or chargrill on medium heat and lightly oil the grill plate. Remove chicken wings from sauce; grill until lightly browned, about 5 minutes each side.
Pour sauce into a saucepan. Bring to a simmer; cook for 5 minutes.
Preheat oven to 180 degrees C. Arrange chicken wings in a single layer in a large baking dish; pour sauce on top.
Bake in the preheated oven, turning and basting frequently, until wings are browned, about 1 hour.
Substitute cooking sherry for the sake if preferred.