Soak wooden skewers in water for at least 20 minutes to prevent them from scorching on the grill.
In a medium mixing bowl, whisk together the gochujang paste, tamari, toasted sesame oil, grated ginger, minced garlic, sea salt, and black pepper until smooth.
Slice the pork tenderloin and pork belly into uniform 1-inch cubes and toss them in the gochujang marinade until every piece is thoroughly coated.
Thread the marinated pork onto the skewers, alternating with chunks of red bell pepper and 1-inch pieces of green onion.
Heat a grill pan or outdoor grill to medium-high heat and lightly grease the grates with a high-heat oil.
Grill the skewers for 3 to 4 minutes per side, turning carefully, until the pork is cooked through and has a beautiful smoky char.
Transfer the skewers to a plate and let them rest for two minutes before serving to ensure the meat stays juicy.