It was an early summer morning in the Ventus Kingdom. The first prince, Socious, had turned twenty years old. To complete his coming-of-age ceremony, he had to establish a contract with a monster by the end of the day. Otherwise, he would not be recognized as a proper adult. Leading four guardian knights arranged by his father the king, Socious rode his horse towards the deep forest stretching east of the royal capital. Near the entrance of the forest, traps set by his father should be scattered about, the plan being that if they were lucky, a weak monster might have been caught in them.

The guardian knight replied, "There is no mistake." Then, after proceeding a little further, they found the traps set by his father the king. They were magic formulas that slowed monsters down and immobilized them; there were several in total. At first, all the traps were empty.