In the year 20xx AD, insects have become resistant to every kind of insecticide. In order to create an effective pest control, the Japanese company Mars Pharmacy develops a small insect-terminating robot - the 11.5 cm tall maid type robot Hoihoi-san. Dewa Kimiko, who works for a pharmacy always loved dolls, and bought Hoi Hoi-san soon after release. Little did she expect her peaceful slumber at home to be disturbed by her robot's vehement bursts of gunfire - exterminating insects. So she tends to be annoyed by robot-fan customers. To top things off, another small robot type named Combat-san - belonging to a frequent pharmacy customer - fights a nightly all-out war against Kimiko's Hoi Hoi-san - loosing every time.