Soak wooden skewers in water for 20 minutes to prevent burning on the grill.
Cut the pork tenderloin and pork belly into uniform 1-inch cubes.
In a medium mixing bowl, whisk together the gochujang, tamari, toasted sesame oil, honey, minced garlic, and grated ginger.
Add the pork cubes to the bowl and toss until every piece is thoroughly coated in the marinade; let rest for 15 minutes.
Thread the pork onto the skewers, alternating between the lean tenderloin and the richer belly pieces.
Preheat a grill or cast-iron grill pan over medium-high heat and lightly brush with a tiny bit of oil.
Grill the skewers for 3 to 4 minutes per side, or until the pork is cooked through and the edges are slightly charred and caramelized.
While the pork is grilling, toss the sliced cucumber with rice vinegar, sea salt, and black pepper in a small bowl.
Serve the hot, spicy skewers immediately alongside the chilled cucumber salad.