Place a large Dutch oven over medium heat. Add chicken and cook until browned, about 10 minutes. Drain and discard fat.
Mix soy sauce, water, garlic, sesame oil, and sesame seeds together in a large bowl. Add sugar to taste, remembering you can always add more, but you can't take away. Stir to mix well and dissolve sugar. Fold in potatoes, carrots, and onion. Season with pepper.
Pour vegetables into the Dutch oven to cover chicken. Cover with a lid and bring to a boil, about 5 minutes. Stir and reduce heat to medium for about 5 minutes. Reduce heat to low and simmer 40 minutes more, stirring occasionally.
Serve chicken and vegetables over hot cooked rice.
