Place all the marinade ingredients in a bowl and mix well. As Mirin is alcoholic, you can replace it with Sugar. In this case, you use 3 tablespoons Sugar in total.
Add the vegetables and combine.
Cut the fish fillets into smaller pieces, about 2cm thickness, remove bones if necessary. Season with Salt & Pepper, then coat with Potato Starch Flour.
Heat Oil in a large saucepan over medium-high heat.
Cook the fish pieces for 2 minutes, turning halfway through cooking, or until cooked through. Transfer to the marinade & vegetable mixture. Combine evenly and set aside for 1 hour.
You can do the process using a serving bowl, so that you can serve straight away. Otherwise, arrange the mixture on a serving plate or bowl and enjoy with freshly cooked rice.
