Kokushi Musou!!

There is a hidden island that is a mecca for martial artists. There are different reasons people go there--because they want to become amazing at their art, or simply because they come from a family known for martial arts and they are sent there by their parents. In any case, new arrivals sign a contract that they can't leave for 10 years, and that contract is strictly enforced. Within the complex, there is a forbidden area...