In a large bowl or resealable bag, combine soy sauce, sriracha, minced garlic, ginger, toasted sesame oil, red chili flakes, salt, and pepper. Add your cut chicken thighs, making sure they are well-coated in the marinade. Cover the bowl or seal the bag tightly, then refrigerate for at least 2 hours or up to 8 hours for maximum flavor absorption.

Approximately 15 minutes before you're ready to grill your chicken, preheat your grill to medium heat, targeting a temperature of 375-400°F. Make sure the grates are clean and lightly oiled.

While the grill heats up, prepare your garnishes. Mince fresh green onions and set them aside. In a small skillet over medium heat, toast sesame seeds for 3-5 minutes until golden.

Retrieve the marinated chicken and arrange the pieces on the preheated grill. Grill for 10-12 minutes, flipping every 2-3 minutes. In the last 2 minutes, brush the chicken with your Japanese BBQ sauce.

Check the chicken’s internal temperature with an instant-read thermometer to ensure it reaches at least 165°F.

Once cooked, transfer the chicken to a serving platter. Sprinkle toasted sesame seeds and minced green onions over the top. Serve alongside extra BBQ sauce and yum yum sauce for dipping.