Whisk together soy sauce, sugar, ginger, vinegar, sesame oil, red pepper, and garlic. Pour into a resealable plastic bag and place pork in bag. Securely seal bag and chill for at least 8 hours or overnight; flip bag a few times.
Preheat oven to 425 degrees F.
Heat a large oven safe frying pan coated with cooking spray over medium-high heat. Take pork out of bag, saving liquid, and lay in pan. Cook 6 minutes, being sure to brown on all sides.
Move pan to oven and cook 15 minutes or until pork is fully cooked, a meat thermometer should read at least 160 degrees F. Let rest 5 minutes before slicing.
Pour the saved marinade in a small pot and let boil. Lower heat and simmer 5 minutes.
When ready to serve, slice pork into thin pieces and spoon sauce overtop.