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 fully incorporated.
02 - Measure out 1/2 cup of the marinade and transfer to a separate container for basting during grilling. Set aside.
03 - Place chicken pieces in a large resealable bag or shallow dish. Pour the remaining marinade over the chicken, ensuring all pieces are thoroughly coated. Seal or cover and refrigerate for at least 2 hours, or overnight for maximum flavor.
04 - Heat grill to medium-high temperature, approximately 400°F. Lightly oil the grates to prevent sticking.
05 - Remove chicken from the marinade and discard the used liquid. Pat the chicken pieces dry with paper towels to promote better charring.
06 - Place chicken on the grill skin side down. Cook for 6-8 minutes until well-marked, then flip and cook for another 6-8 minutes.
07 - Brush chicken with the reserved marinade. Continue grilling, turning and basting every 2-3 minutes, until the chicken reaches an internal temperature of 165°F and develops a caramelized exterior, approximately 20-25 minutes total grill time.
08 - Transfer chicken to a platter and let rest for 5 minutes to allow juices to redistribute. Garnish with sliced scallions, toasted sesame seeds, and fresh pineapple pieces if desired. Serve immediately.