Long ago in the Land of Peace, invaders invaded. They came from the realms of Magical Lands and their goal was to disrupt the peace and overthrow the existing kingdom and then to rule.
They abducted the people and ordered them to be their followers. Whoever refused was executed. Those who accepted were taken one by one and then sent to a secret place and added, "Overthrow" is your identity, they put a mark on their foreheads and then released them.
When they succeeded in gaining many followers, they decided to capture the royal palace and to kill the King.