Grate ginger root. In a bowl mix ginger, soy sauce, Sake, and Mirin. Set aside.
If you are using a pork loin chunk, slice into 1/16" (2mm) thickness.
Heat a frying pan at medium high heat and add oil, then add sliced pork to pan-fry. Cook in a single layer on both sides until brown. Add the ginger sauce to the pan and cook for a minute to coat the meat with the sauce.