Fifteen years ago, a city in Japan crumbled and was cut out from the light of the surface for as long as people could remember. From where the city once stood, an ominous tower rose and beneath it was a living prison which possessed a desire for blood, lust and sleep. This prison was called the "Jail".
The Jail gave birth to creatures called the Marchens, beings that captured humans and imprisoned them in the Jail's wards. For what seemed to be an eternity, the humans were tortured by their captors-day in day out-all so that the Jail's desires could be fulfilled.
However, within the confines of the Jail was an organization called the Dawn which sought to free the people from their suffering and to escape from the Jail. Among the members of the Dawn were a group of youths who possessed the power to fight the Marchens-A boy named Jack and a group of girls called the Blood Maidens.
Together with their friends from the Dawn, Jack and the Blood Maidens fought against the wardens of the Jail, the Nightmares, and rescued the humans held captive by the Marchens. After going through various perils and challenges, Jack and his friends climbed atop the Jail's tower and faced the mastermind behind the Jail-An otherworldly being called the "Snark" who had taken up the identity of Dawn's deceased founder, Professor Tohjima.
In the final confrontation between Jack's group and the Snark, the latter merged himself with the Jail and turned into a monstrous entity bent on destruction. However, with the help of an angelic being born from the desire to save the world, Jack and his friends were able to defeat the Snark and destroyed the tower they stood on.
Jack and his friends' efforts marked the end of the peoples' confinement in the Jail. With the tower destroyed and the Snark defeated, the angel led everyone to the surface world. Having fulfilled her mission, the angel left and watched over the world.
And it was at that point that things began to turn out for the better for everyone.
As soon as everyone set foot onto the surface world, they were greeted by people from neighboring cities and rescue workers, all of whom have prayed for the safety of those who were caught in the disaster from fifteen years ago. Those who saw their family members reunited with them instantly. Those who did not were assisted by the rescue workers in reaching home.
The members of the Dawn including Jack and the Blood Maidens were sent to a governmental organization in Japan called the National Defense Bureau. There, Haru and Miko, two of the Dawn's members as well as Jack's friends, explained the experiences that the people endured during their time in the Jail.
After a long period of discussion, the National Defense Bureau agreed to help the Dawn in rebuilding the city destroyed by the Jail as well as to prevent future threats related to it. In addition, the Bureau, at Haru's request, will conceal the identity of Jack and the Blood Maidens from the public so as to enable them to live a normal peaceful life.
From there onwards, everyone began to pursue their own course of action. The Dawn established itself in the National Defense Bureau and worked together with them. The Order of the Sun, led by Michiru and Hitsuka, travelled around Japan to tend to those in need.
As for Jack and the Blood Maidens, they were sent to the small town of Wonder Ville along with a member of the Dawn, Doctor Shirosagi, who volunteered to be their guardian. There, Jack and the girls enroll themselves as students in the town's local high school, Shinzo Academy.
A new tale of wonders and adventure begins for Jack and his company…