In a large mixing bowl, whisk together soy sauce, brown sugar, honey, sesame oil, garlic, ginger, rice vinegar, gochujang, and black pepper until smooth.
Add the chicken pieces to the marinade and toss until every piece is evenly coated.
Cover the bowl and refrigerate for at least 2 hours, or overnight for the best flavor.
If using wooden skewers, soak them in water for 30 minutes before assembling.
Thread the marinated chicken onto the skewers, leaving a little space between pieces for even cooking.
Preheat a grill to medium-high heat and lightly oil the grates.
Place the skewers on the grill and cook for 10 to 12 minutes, turning every few minutes.
Brush the skewers with additional marinade during the final few minutes of cooking if desired.
Cook until the chicken reaches an internal temperature of 165°F (74°C) and develops caramelized edges.
Transfer to a serving platter and sprinkle with sesame seeds and green onions before serving.