The story begins in the near future, where a social mobile network called the "Kizuna-Topia" (Bonds-Topia) controls all communication and surveillance in the wall-bound city.
In this city, two sisters, Enna and Yayako, come face to face with the ongoing man-hunt for young, healthy children. The kidnappers take these kids to the white tower to extract their brains and sell their bodies. This man-hunt, led by the local police known as the "Jikei," is counteracted by the mysterious being only known as "The Witch." Enna, Yayako, and other residents of this city are trapped between the ongoing conflict between the Jikei and The Witch.

When they were young, Suzu and Midori were separated as Midori moved away. Suzu grew up and has become a builder of robots and anything else mechanical she can get her hands on. One fateful morning her favorite electronics shop is closed so she goes off to relax while waiting for the shop to open when Midori calls again, after all these years, wanting to take up where they left off. Suzu is ecstatic about this – they had so much in common when they were young. Only Midori has opened up a Maid Café.