Soak up the water from the mackerel using paper towels, and for those who care to, remove the bones.
Cut an mackerel into the skin side of the fillet.
Boil a bit of water and pour over the fillet.
Mix the miso, mirin, sugar, soy sauce, and ginger in a separate bowl. In a frying pan, add the mackerel and enough water to cover it.
Add the mixed ingredients and turn on the stove to medium heat.
When the water begins to boil, cover the ingredients with a small lid or tin foil and let it sit.
Once about half the water has evaporated, turn off the heat and serve.