In a mixing bowl, whisk together the soy sauce, brown sugar, pineapple juice, ketchup, and vegetable oil until smooth. Then, add the minced ginger, garlic, rice vinegar, and black pepper, blending everything well.

Place the boneless, skinless chicken thighs in a resealable bag or shallow dish and pour the marinade over them. Ensure that each piece is evenly coated for maximum flavor. Seal the bag or cover the dish, then refrigerate for at least 1 hour or ideally overnight.

About 15 minutes before you’re ready to cook, preheat your grill to medium-high heat, aiming for a temperature of around 375°F (190°C).

Take the marinated chicken out of the refrigerator and let it sit for about 10 minutes at room temperature. Allow excess marinade to drip off.

Place the chicken thighs on the preheated grill, cooking for 6-8 minutes per side. Use tongs to flip the chicken only once.

For an extra layer of flavor, brush the chicken with the remaining marinade during the last 2-3 minutes of grilling.

Once grilled to perfection, remove the chicken from the grill and let it rest on a cutting board for about 5 minutes.

Finally, slice the chicken and serve it topped with chopped green onions and a sprinkle of sesame seeds.