Soak wooden skewers in water for 20 minutes to prevent burning.
Cut the pork tenderloin and pork belly into uniform 1-inch cubes.
In a small bowl, whisk together the gochujang, tamari, sesame oil, honey, grated ginger, minced garlic, and rice vinegar.
Place the pork cubes in a glass bowl and toss with the marinade until thoroughly coated, then let rest for 15 minutes.
Thread the pork onto the skewers, alternating between the lean tenderloin and the rich pork belly pieces.
Preheat a grill pan or outdoor grill to medium-high heat and lightly brush with a high-smoke point oil.
Grill the skewers for 3 to 4 minutes per side, ensuring a deep char develops while the pork reaches an internal temperature of 145 degrees Fahrenheit.
Remove from heat and garnish with toasted sesame seeds and thinly sliced green onions before serving.