Ayuko is left alone at home while her parents travel abroad. Her childhood friend Isao and his bandmate Utsuho show up and their limited-time only sleepover begins.

Maki Asano works as a secretary in the Teito Heavy Industries Development Secretariat. However, that is just her public face, and Maki's real job is as a special secretary directly under an executive. Maki receives a mission from the managing director to "recover important secrets that have been leaked," and she begins her investigation with her partner, former detective Kawasaki...