01 - In a medium bowl, whisk together the soy sauce, mirin, honey, vegetable oil, rice vinegar, minced garlic, grated ginger, sesame oil, and black pepper until well combined. Reserve ¼ cup of the marinade and set aside for basting during grilling.
02 - Place the sirloin cubes in a large zip-top bag or shallow dish. Pour the remaining marinade over the steak, seal tightly, and refrigerate for at least 1 hour or up to 8 hours for deeper flavor penetration.
03 - If using wooden skewers, submerge them in water for at least 30 minutes to prevent burning on the grill.
04 - Preheat an outdoor or indoor grill to medium-high heat. Lightly oil the grill grates to prevent sticking.
05 - Thread the marinated steak cubes and prepared vegetables alternately onto the skewers, distributing the ingredients evenly across each skewer for balanced cooking.
06 - Place the skewers on the preheated grill and cook for 4 to 6 minutes per side, brushing with the reserved marinade and turning occasionally, until the steak reaches your desired doneness and the vegetables develop a light char.
07 - Remove the kabobs from the grill and sprinkle with sesame seeds and chopped green onions if desired. Serve immediately while hot.