Cut the pork loin into 1-inch cubes and place them in a medium glass bowl.
In a small jar, whisk together the gochujang, tamari, sesame oil, grated ginger, and minced garlic until smooth.
Pour the marinade over the pork, tossing to coat every piece, and let it sit for at least 20 minutes.
Thread the marinated pork onto wooden or metal skewers, leaving a small space between each cube for even cooking.
Heat a grill pan or outdoor grill over medium-high heat and sear the skewers for 3-4 minutes per side until charred.
While the pork cooks, toss the sliced cucumbers with rice vinegar, sea salt, and red pepper flakes in a small bowl.
Plate the hot skewers over the chilled cucumber salad and garnish with a sprinkle of sesame seeds.