Soak wooden skewers in water for at least 20 minutes to prevent burning.
Cut the pork tenderloin and pork belly into uniform 1-inch cubes.
In a medium bowl, whisk together the gochujang, tamari, honey, toasted sesame oil, rice vinegar, minced garlic, and grated ginger.
Add the pork cubes to the marinade, tossing well to coat, and let sit for 15 minutes.
Slice the red bell pepper into 1-inch squares and cut the green onions into 1-inch lengths.
Thread the marinated pork and vegetables onto the skewers, alternating between the lean tenderloin, the rich pork belly, and the fresh vegetables.
Preheat a grill pan or outdoor grill over medium-high heat and lightly oil the grates.
Grill the skewers for 3 to 4 minutes per side, or until the pork is cooked through and the edges have a beautiful charred finish.
Remove from heat and sprinkle with sesame seeds before serving hot.