Preheat the oven to 180C degrees.
Mix the ginger, sesame oil and Kikkoman in a bowl.
Put the fish (skin-side down) into an oven-proof dish then pour over the mixture, covering the fish well.
Cut the lemon in half - squeeze one half over the fish, then cut the other half into 4-6 thin rings.
Season the fish with pepper then lay 2-3 slices of lemon on the fish.
Cover the dish with foil and bake for 20 minutes until the fish flakes easily with a fork.
Serve warm with your chosen side dish and a chilli sauce perhaps.