Cut the cleaned mackerel into thirds and make small slits. Pat dry with a paper towel and sprinkle with pepper.

Place 2 tbsp of flour in a plastic bag, add the mackerel, and shake to coat evenly.

Heat a pan with a small amount of oil and fry the mackerel until golden on both sides.

In a pot, mix 1 cup water, 4 tbsp soy sauce, 4 tbsp mirin, 1 tbsp sugar, and 1/2 tbsp minced garlic. Bring to a boil.

Pour the sauce over the fried mackerel gradually and simmer until the fish is coated in a brown glaze.