Whisk together soy sauce, mirin, sake, sugar, grated ginger, and minced garlic in a bowl to create the teriyaki sauce.

Cut chicken thighs into 1-inch pieces and marinate them in half of the teriyaki sauce for at least 10 minutes.

Heat oil in a large skillet over medium-high heat, then add the chicken and cook for 5-7 minutes until browned.

Pour in the remaining teriyaki sauce and simmer for another 5-7 minutes, stirring occasionally, until the sauce thickens and coats the chicken.

Serve the classic teriyaki chicken over steamed rice and garnish with sesame seeds and chopped green onions.

For a spicy variation, add a teaspoon of sriracha or red pepper flakes to the sauce.

To make it citrusy, squeeze in a tablespoon of orange or lime juice at the end of cooking.

For a sweet and savory option, add a tablespoon of honey or maple syrup to the sauce while simmering.