01 - Whisk together soy sauce, pineapple juice, brown sugar, ketchup, rice vinegar, ginger, garlic, sesame oil, honey, smoked paprika, and pepper in a large bowl until thoroughly combined and sugar is dissolved.
02 - Measure out 1/2 cup of the marinade and transfer to a separate container for basting during grilling. Keep covered and refrigerated until ready to use.
03 - Place chicken pieces in a large resealable bag or shallow dish. Pour remaining marinade over the chicken, ensuring all pieces are evenly coated. Seal or cover and refrigerate for at least 2 hours, preferably overnight for maximum flavor penetration.
04 - Heat grill to medium-high temperature, approximately 400°F. Clean grates thoroughly and brush with oil to prevent sticking.
05 - Remove chicken from marinade and discard the used liquid. Pat chicken pieces dry with paper towels to promote proper searing and reduce flare-ups.
06 - Arrange chicken skin-side down on the preheated grill. Cook for 6-8 minutes until skin is well-marked and beginning to crisp, then flip and continue grilling for another 6-8 minutes.
07 - Begin brushing chicken with the reserved marinade, turning and basting every 2-3 minutes. Continue grilling until chicken reaches an internal temperature of 165°F and develops a rich caramelized coating, approximately 20-25 minutes total grilling time.
08 - Transfer grilled chicken to a serving platter and let rest for 5 minutes to allow juices to redistribute. Garnish with sliced scallions, toasted sesame seeds, and diced pineapple. Serve immediately while hot.