Cut the green onion lengthwise, remove the core, and slice thinly. Soak in water and gently rub. Drain thoroughly after 5 minutes to make shredded green onion.

Heat salad oil in a frying pan over medium heat. Add pork belly slices and cook until browned on both sides.

Remove excess oil with a paper towel, then add the seasoning mixture (sake, mirin, sugar, soy sauce). Cook until the sauce thickens while stirring.