Slice the pork loin into 1-inch cubes and set aside in a medium mixing bowl.
In a small bowl, whisk together the gochujang, tamari, sesame oil, honey, minced garlic, and grated ginger until smooth.
Pour two-thirds of the marinade over the pork cubes, tossing to coat thoroughly, and let marinate for at least 20 minutes.
Thread the marinated pork onto wooden or metal skewers, leaving a small space between each piece for even cooking.
Preheat a grill pan or outdoor grill to medium-high heat and lightly grease with a small amount of oil.
Grill the skewers for 3-4 minutes per side, brushing with the remaining marinade during the last 2 minutes of cooking until charred and cooked through.
Thinly slice the cucumber and toss with rice vinegar and sliced green onions in a small side bowl.
Garnish the skewers with sesame seeds and serve immediately alongside the chilled cucumber salad.