This is a Hawaiian dish that uses a Chinese cooking method with Japanese ingredients. You can literally find 100s of Shoyu chicken recipes in Hawaii and every household has it's own twist. The key if you want to be "authentic" is to use Hawaiian Shoyu, it's a bit sweeter than normal soy sauce (Shoyu means soy sauce in Japanese) which you can find in any Asian market. The basics of Shoyu chicken is poaching the chicken in soy sauce and other ingredients. If you like teriyaki chicken the flavor profile is very similar. I have friends that use Teriyaki sauce in their Shoyu chicken recipes.