Combine the soy sauce, mirin, yuzu juice, sugar, grated ginger, and minced garlic in a small saucepan.
Cook the mixture over medium heat, stirring occasionally until the sugar completely dissolves, about 3-4 minutes. Allow it to simmer gently for another 5 minutes until slightly thickened. Remove from heat and let cool.
Preheat the grill or grill pan over medium-high heat.
In a mixing bowl, toss the chicken pieces in vegetable oil, and season with salt and pepper.
Thread the chicken pieces onto skewers, leaving a little space between each piece for even cooking.
Grill the chicken skewers for about 5-7 minutes, turning occasionally. Brush generously with the yuzu yakitori tare during the last few minutes of cooking.
Ensure the chicken is fully cooked to an internal temperature of 165°F (75°C).
Once grilled, remove the skewers from heat and garnish with chopped green onions.
Serve hot with additional yuzu tare for dipping, if desired.