Place ribs into a resealable plastic bag. Use two bags if needed. Combine marinade mixture and pour over ribs. Let the air out of the bag and massage ribs to work the marinade. Place into the refrigerator for 2-4 hours.
Combine water with mirin, brown sugar, rice wine vinegar, honey, and fish sauce. Let mixture stand for 10 minutes.
Heat oil in a skillet. Place 5 ribs into skillet and brown on all sides, about 2-3 minutes total. Remove and place them onto a clean plate. Repeat the process until all the ribs are browned.
Add braising liquid to a large pot and bring to a simmer. Add ribs, cover, and cook over medium-low heat for 20 minutes.
Remove lid and continue cooking for an additional 20-25 minutes until braising liquid is thick and caramelized. Turn ribs every 8-10 minutes to coat evenly.
Once cooked through (internal temperature between 175-180 degrees F.), remove ribs from the pot and place them onto a serving dish. Spoon the remaining sauce onto ribs and garnish with chopped green onion.