Cut the fat out from the chicken thighs and chop it to bite size pieces.
Boil 2 cups of water and place the chicken thighs in it. Let the chicken boil for 5 minutes.
Strain the chicken stock into another bowl and set the chicken aside.
Combine chicken stock, soy sauce, sugar, garlic, and ginger, and bring it to a boil. This is the teriyaki sauce base.
Combine potato starch and water to create a slurry and add to the teriyaki base. Mix while adding to prevent it from clumpling.
Bring the sauce to a boil until it becomes thick. Turn off the heat.
In a separate pan, saute the chicken until it is lightly browned.
Add the onion and peppers, and saute them together for a couple of minutes.
Drizzle in the sauce, mix it well until everything is coated.
Taste and adjust with more sauce as needed.
Plate and serve with freshly cooked rice or boiled udon. Enjoy!