From the introduction:
Ten years ago, four maidens were appointed as the apprentices of an old mage named Ragishss, they were trained as mages and were supposed to become the guardians of the city, helpers in the times of need and defenders from those who would seek to do the town harm. However, just before completing their training, the girls suddenly rebelled against Ragishss and killed him. During the harsh magic battle, the entire town was entombed underground and a barrier spell was placed on it, preventing anyone from leaving, including the maidens who terrorized the town. The four maidens were soon to be known as The Four Witches of Kathtom.
You arrive a little before the adventurer Rance enters the city, prepared to save the day and lay as many beautiful women as he can.