Add the 1 cup of water, soy sauce, brown sugar, honey, ginger, garlic and mirim to a small saucepan and whisk together.
Bring the mixture to a boil over medium heat.
Meanwhile, add the cornflour and ¼ cup cold water to a small bowl and whisk together.
Slowly add the cornflour mixture to the boiling sauce.
Reduce the heat to medium-low and continue cooking, whisking often, until the sauce has thickened to your desired consistency. This should take around 5 minutes.
Nutritional information is an estimate and provided as a courtesy. The values may vary according to the ingredients and tools that are used. Please use your preferred nutritional calculator for more detailed information.