Whisk soy sauce, honey, rice vinegar, sesame oil, garlic, ginger, black pepper, and red pepper flakes until smooth. Reserve 3 tablespoons for glazing.

Place drumsticks in a bag with the remaining marinade, coat well, and marinate 30 minutes at room temperature or up to 4 hours refrigerated.

Grill over medium heat (375°F to 400°F) for 5 to 6 minutes per side until the skin has grill marks and releases easily.

Move to cooler part of grill, brush with reserved marinade, and cook 15 to 20 minutes with lid closed, turning once until the chicken reaches 170°F and the glaze is sticky.

Rest 4 to 5 minutes on a platter, then pile up and serve warm.