For two decades now, Earth has been home to enigmatic creatures called Kaiju. These monsters, whose origin is unknown, were initially aggressive until it was discovered that their hostility could be quelled by the voice of a young girl. Thus, humanity took the bold step of trying to keep them as companions.
To this end, the Tatara girls' school introduced a unique program where young girls could train as Kaiju trainers. Ion Hidaka, a sixth-grader, decided to pursue this unconventional career. As a member of the breeding club, assigned at the start of the school year, Ion has to take care of a colossal monster that lives in the forest behind the school every day.
