In the other world of Lockenheim, the Demon King Barbados and the hero Cygnar, rivals by fate, are transported to the present day by a time-space distortion caused by their battle - and the entire Demon King's castle is transferred to the present day. And, to their surprise, the land where they were transported is a planned condominium construction site in Tokyo's Koto Ward! A skilled (?) Demon King who has decided to manage the Demon King's Castle as a condominium.