Claes is a girl training to become the "Machuu Tsukai" - the Demon Bug Tamer. They have the unique power to communicate with and command various insects. Their job is the extermination of Demon Bugs that harm humans. However, in recent years, waves of insects continue to invade the land and the damage caused by them is constantly getting bigger.

One day, a girl called Lily came to Claes and asked her to exterminate a small bug that was bothering her village. She accepted her first job and followed Lily. However, the small insect wasn't the only Demon Bug that the girls have encountered...