Follow these steps to create Juicy Japanese Chicken Yakitori that will impress everyone:

1. Prepare the Marinade: In a bowl, whisk together soy sauce, mirin, sake, brown sugar, garlic, and ginger until the sugar dissolves.
2. Marinate the Chicken: Cut the chicken thighs into bite-sized pieces and add them to the marinade. Allow them to marinate for at least 30 minutes, or up to 2 hours for deeper flavor.
3. Prepare Skewers: If using wooden skewers, soak them in water for 30 minutes to prevent burning on the grill. Metal skewers can be used directly.
4. Assemble the Skewers: Thread marinated chicken pieces onto the skewers, alternating with pieces of green onion and red bell pepper for added flavor and color.
5. Preheat the Grill: Preheat your grill or grill pan over medium-high heat. Brush the grill with vegetable oil to prevent sticking.
6. Grill the Skewers: Place the skewers on the grill. Cook for about 5-7 minutes on each side, brushing with remaining marinade occasionally, until the chicken is cooked through and has grill marks.
7. Check for Doneness: Ensure the chicken reaches an internal temperature of 165°F (75°C) for safe consumption.
8. Garnish: Once cooked, remove from the grill and let rest for a couple of minutes. Sprinkle with sesame seeds and chopped green onions for garnish.
9. Serve: Arrange the skewers on a platter for serving.

These steps will guide you in creating Juicy Japanese Chicken Yakitori that is delicious and visually appealing.