The seal of the passage between the two realms of the underworld has been loosened again after a hundred years, but this time it is no accident. A conspiracy starting from the Demon City Academy is quietly unfolding. What no one in the underworld expected was that the passage of time had brought about some unexpected changes, making their plan that they thought was seamless have deviated from the planned track... This is where the adventure of Gu Han and his friends begins.