Cut the chicken thigh meat into 3/4 inch cubes. Cut the scallions crosswise into 3/4 inch pieces. Heat the grill. Thread chicken and scallion pieces onto the skewers, alternately.
Make the Sauce: In a small pot combine the saki, mirin, garlic, ginger, red pepper, sugar and soy sauces. Simmer for 5-10 minutes, until sauce is reduced by about one quarter.
Grill the skewers for 2 minutes. Brush with sauce and turn, brush with sauce on the other side. Grill for 5-8 minutes more, brushing with sauce every 2 minutes, until the chicken is cooked through and glazed.
If you can find these ingredients, serve yakitori with sansho and Japanese 7 spice to sprinkle on top.