Cut the pork tenderloin and pork belly into uniform 1-inch cubes.
In a medium bowl, whisk together the gochujang, tamari, toasted sesame oil, rice vinegar, honey, grated fresh ginger, and minced garlic.
Toss the pork cubes in the marinade until well-coated and let them marinate for at least 15 minutes.
Thread the pork onto skewers, alternating between the lean tenderloin and the rich pork belly pieces.
Heat a grill pan or outdoor grill over medium-high heat and lightly grease with a touch of oil if needed.
Grill the skewers for 3-4 minutes per side until the pork is cooked through and the edges are beautifully charred.
While the pork cooks, thinly slice the cucumber and green onions, then toss them in a small bowl with the sea salt and black pepper.
Serve the hot, spicy skewers immediately over the chilled cucumber salad for a refreshing contrast.