Combine soy sauce, brown sugar, pineapple juice, sake, rice vinegar, garlic, ginger, monosodium glutamate, red pepper 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 grill for medium heat and lightly oil the grate. Remove chicken wings from sauce; grill until lightly browned, about 5 minutes per side.

Pour sauce into a saucepan. Bring to a simmer; cook for 5 minutes.

Preheat oven to 350 degrees F (175 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.