In a medium bowl, whisk together soy sauce, honey, rice vinegar, minced garlic, grated ginger, sesame oil, and black pepper to create the marinade.
Place the chicken thighs in a resealable plastic bag or shallow dish and pour the marinade over the chicken. Seal the bag or cover the dish and refrigerate for at least 30 minutes, or up to 2 hours for more flavor.
Preheat your grill or a skillet over medium-high heat. Remove the chicken from the marinade and discard the marinade.
Cook the chicken for about 6-7 minutes on each side, or until fully cooked and internal temperature reaches 165°F.
While the chicken is cooking, prepare the rice according to package instructions if not already cooked.
Once the chicken is done, let it rest for a few minutes before slicing it into strips.
To assemble the bowls, divide the cooked rice among four bowls, top with sliced chicken, and garnish with chopped green onions and sesame seeds if using.