Heat sake, vinegar, and mirin to a boil over medium high heat.
Reduce heat to medium low, and add brown sugar and soy sauce. Then, reduce heat to low and add miso paste. Continue simmering until miso paste has completely dissolved.
Let marinade cool before pouring over protein. Marinate protein for 30 minutes up to 4 hours.
To make into a thicker glaze, heat marinade over medium low and add a slurry of 1 tbsp cornstarch to 1 tbsp water.