This is a basic sauce which can be used all summer for grilling chicken. Yakitori is usually chicken on skewers: yaki=grilling and tori=chicken. Yakitori/焼き鳥/grilled chicken
As you are grilling dip the skewered chicken parts into this sauce then let the excess liquid drip back into the pan to flavor both the sauce and the chicken.
Some yakitori restaurants in Japan claim to have been using their sauce for years, adding saké, mirin, and shoyu when needed. That extra chicken-y-ness makes for their “secret” illusive deliciousnes…
Tare: basic sauce for Japanese grilling
from: The Japanese Kitchen
•250 Recipes in a Traditional Spirit•
by Hiroko Shimbo
page 405
makes 1½ cups sauce
- 10-12 chicken wings (separated at the joints)
- ¾ cup sake
- 1⅓ cups mirin
- 3 Tablespoons sugar
- 1⅓ cups shoyu
In a medium pot, bring the sake and mirin to a boil over high heat. Reduce the heat to medium, add the sugar, and cook until the sugar is dissolved. Stir to prevent burning.
Add the shoyu and chicken wings, and bring the mixture to a boil. Cook over low heat for 30 minutes. At the end of the cooking, the sauce will be thick and glossy.
Strain the sauce through a strainer lined with cotton cloth, discarding the wingtips. The other parts of the wing are quite tasty.
Let the sauce cool to room temperature, then refrigerate for as long as a month. Reheat the tare before using it, and once every week between uses. Or freeze it.
This tare (basic sauce) can be used for more than simply flavoring yakitori (chicken skewers). All summer you can use portions of the sauce to grill: chicken, pork, fish, or just about anything you can cook over charcoal, food you cook on skewers, or not! Add some orange juice, honey, fruit preserves, spices, or other flavorings and voila: teriyaki sauce.
Tess's Japanese Kitchen 
Looks good!
Yes, and the sauce is versatile because you can add spices, fruit juice, jam or chutney to portions of it and you’ll quickly have a completely original teriyaki sauce. I make it every year!