In a small bowl, mix soy sauce, mirin, sugar, grated garlic, and grated ginger. Set aside.
Cut the chicken thighs into 24 equal pieces. Aim for similar size so they cook evenly.
Thread 4 pieces onto each skewer, keeping the skin facing the same side. Make 6 skewers total.
Sprinkle both sides lightly with salt and black pepper.
Heat cooking oil in a frying pan over medium heat. Place the skewers skin-side down first, cover with a lid, and cook for about 3 minutes per side until cooked through and lightly browned.
Lower the heat to medium-low. Pour the sauce over the chicken and continue cooking for about 2 minutes, turning the chicken until the sauce gets glossy and slightly thickened.
Scoop cooked rice into two plates. Place the glazed yakitori on top and spoon any extra sauce over the rice.
