Prepare the Tare Sauce: In a small saucepan, combine soy sauce, mirin, sake, and sugar. Bring to a simmer over medium heat, stirring until sugar dissolves. Reduce heat to low and simmer for 10-15 minutes, or until the sauce slightly thickens to a glaze consistency. If using, add grated ginger during the last 5 minutes. Set aside.

Prepare the Chicken Skewers: Thread the chicken pieces onto the soaked bamboo skewers, ensuring not to overcrowd them. Aim for 3-4 pieces per skewer.

Preheat Grill: Preheat your grill or grill pan over medium-high heat. Lightly brush the grill grates or pan with oil to prevent sticking.

Grill Yakitori: Place the skewers on the preheated grill. Grill for 8-10 minutes, turning occasionally, until the chicken is golden brown and nearly cooked through.

Glaze with Tare: During the last few minutes of grilling, brush the yakitori generously with the prepared tare sauce several times, allowing it to caramelize and form a beautiful, glossy coating. Continue turning until all sides are glazed and the chicken is fully cooked (internal temperature 165°F/74°C).

Serve: Serve the hot yakitori immediately with steamed rice or as an appetizer. You can also offer extra tare sauce on the side for dipping.