Thinly slice the onion.
Marinate the pork belly and kimchi with chili powder and sesame oil for about 30 minutes.
Heat oil in a medium to high heat, and stir fry the marinated pork belly and kimchi for 3 minutes.
Add the onion and stir fry for another 3-5minutes until the onion is softened and browned.
Add the sake and soy sauce and continue stir frying.
Sprinkle with small cut chive or spring onion and serve. (optional)