In a bowl, combine soy sauce, brown sugar, ginger, garlic, sesame oil, and black pepper. Mix well.
Add the chicken thighs to the marinade, ensuring they are fully coated. Let it marinate for at least 30 minutes.
Preheat a grill or skillet over medium heat.
Remove chicken from the marinade and reserve the marinade for later.
Grill or sauté the chicken for 6-7 minutes on each side until fully cooked.
In a separate pan, bring the reserved marinade to a boil and simmer for 5 minutes to thicken.
Add pineapple chunks to the pan and cook for an additional 2-3 minutes.
Once the chicken is cooked, place it on a serving platter.
Pour the pineapple sauce over the chicken.
Garnish with sliced green onions and fresh cilantro before serving.