The Maison de Ayakashi, better known as the Ayakashikan, is a high security apartment building where humans with demon ancestors, or yokai, reside, each guarded by their own Secret Service bodyguard. A yokai girl named Ririchiyo Shirakiin moves into the Ayakashikan hoping for some peace and quiet. Instead, she finds herself with the service of the Secret Service agent, Soshi Miketsukami.
The first four volumes of the manga are a prologue. At the end of volume four, a foe possesses Karuta, leaving her in a coma for several months, and uses other yokai to attack the other residents of Maison de Ayakashi. Due to this, nearly every member of the main cast is killed except Rensho, who is currently 41 years old. Part two takes place 23 years later, when those killed are reincarnated. The yokai boy, Mikoto, is still alive as the friend of Watanuki who is now a middle schooler. A time capsule is sent to the past, and now, in the third arc, the story jumps back to the past when they are about to make a time capsule for their future selves.