Wash the mackerels under running water, cut them into serving-sized pieces, and soak them in mirin and soju for 10 minutes. Pat dry with paper towels.

Place 3 tbsp of flour into a disposable bag, add the dried mackerel pieces, and shake to coat evenly.

Shake off excess flour from the mackerel pieces.

Mix 1 tbsp each of mirin, soju, soy sauce, sugar, plum syrup, and minced garlic to prepare the glaze.

Heat oil in a pan and place the mackerel pieces. Cook on medium-low heat until one side is well-cooked.

Flip the mackerel and cook the other side. Use paper towels to remove excess oil from the pan.

Pour the prepared glaze over the mackerel in the pan and reduce the heat to simmer.

Let the glaze simmer and thicken until the mackerel becomes glossy and flavorful.