Combine the water, soy sauce, brown sugar and mirin in large ziploc bag and add the chicken thighs. Seal the bag and let the chicken marinade in the fridge for at least an hour. Remove the chicken pieces from the marinade and pat dry with paper towels.

Heat the oil in a non-stick frying pan over medium heat. Place the chicken skin-side down in the pan and fry until golden brown on one side, about 2 minutes.

Flip the chicken, then add 1 tablespoon of sake and quickly cover the pan with a lid. Steam the chicken until it is just cooked through, about 5 minutes.

Prepare the teriyaki sauce by mixing 2 tablespoons each of: honey, mirin, sake, and soy sauce. Stir to combine.

Turn up the heat to high, and then add the teriyaki sauce. Let this mixture boil, while flipping the chicken repeatedly to coat evenly.

The chicken teriyaki is done when most of the liquid has evaporated and the sauce forms a thick glaze around the chicken. Slice and pour the remaining teriyaki sauce over the chicken.