Put together the marinade by:

The shoyu, brown sugar, water, mirin, garlic, ginger, and sesame oil should be mixed together in a bowl of medium consistency. Until the sugar is entirely dissolved, continue swirling the combination.

For the chicken, marinate it.

Place the chicken thighs in a big plastic bag that can be sealed back up or in a dish that is shallow.

After pouring the marinade over the chicken, make sure that every piece is well covered in the sauce.

Once the bag or dish has been sealed, place it in the refrigerator for at least one hour, but ideally overnight, for the finest possible flavor.

To prepare the chicken:

Preheating a grill pan or a big skillet over medium heat is the first step.

The chicken should be removed from the marinade, and any excess should be allowed to drop off.

The chicken should be cooked for approximately five to seven minutes each side in the hot skillet or on the grill pan. This should be done until the chicken is completely cooked through and has a wonderful caramelized coating. (The temperature can exceed 165 degrees Fahrenheit or 74 degrees Celsius.)

Lower the amount of marinade.

While the chicken is cooking, carefully transfer the leftover marinade to a small saucepan and set it aside.

Turn the heat down to medium-high and bring it to a boil. After that, decrease the heat and let it simmer for around five minutes, or until it has slightly thickened.

Provide:

To finish, slice the chicken that has been cooked and sprinkle the reduced marinade over it.

Using chopped green onions and toasted sesame seeds, garnish the dish.

Serve the shoyu chicken on a bed of cooked rice, and if you so wish, accompany it with a side of vegetables that have been steamed.