Wash the sardines thoroughly under running water, pat dry, and cut into bite-sized pieces. Place them in a bowl, add soy sauce and grated ginger, mix well, and coat with flour.

Cut the eggplants into bite-sized pieces and soak them in water for 5 minutes. Drain well. Slice the green onion thinly and soak in water for 5 minutes, then drain (to make white-hair onion).

Mix the sauce ingredients (sake, mirin, sugar, and miso) in a separate bowl.

Heat salad oil in a frying pan over medium heat. Add the eggplants and stir-fry until softened, then remove them from the pan.

Add the sardines to the pan and cook over medium heat until both sides are browned and cooked through. Use paper towels to remove excess oil.