The Maison de Ayakashi (メゾン・ド・章樫 Mezon do Ayakashi?), better known as the Ayakashikan (妖館?), is a high security apartment building where humans with demon ancestors, or yōkai, live, each guarded by their own Secret Service bodyguard. A yōkai girl named Ririchiyo Shirakiin moves into the Ayakashikan hoping for some peace and quiet. But instead, she finds herself with the service of the Secret Service agent, Sōshi 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 yōkai to assault the other residents of Maison de Ayakashi. Because of this, virtually every person in the principal cast is killed except Renshō, who’s currently 41 years old. Part two takes place 23 years later, when those killed are reincarnated. The yōkai lad, 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 narrative jumps back to days gone by when they have been about to make a time capsule for his or her future selves.