To make the sauce, combine the soy sauce, ginger juice, saké and sugar in a small bowl. Stir until the sugar is dissolved.
Heat 1 tablespoon of the oil in a large skillet over high heat. Stir-fry the pork until the meat is partially cooked, about 1 minute. Remove the pork from the skillet and drain.
Add the remaining oil to the skillet. Stir-fry the c