The series focuses on a professional boxer who chooses to become a manga artist after sustaining an injury. The man takes in two cats: Kuro, who is very timid, and her younger sister Chin.

Najica Hiiragi, perfumer and secret agent, is sent out on a number of recovery missions to round up rogue humaritts, androids with combat abilities. Najica is assigned a humaritt partner, Lila, whom Najica is to groom as an agent and receive assistance from along the way. As Najica grows to accept Lila, each new mission they embark on reveals more and more about the capabilities and mysterious origins of the humaritts. (Source: ANN)

Mayfly reveals Cima's backstory in flashbacks as she reflects on her past prior to the events of Episode 13. It reveals that Cima and her unit poisoned a Side 5 colony using G-3 nerve gas, under orders, but were treated as pariahs afterwards by their own countrymen for committing such an atrocity. At the end of the war her superior refused to let her retreat to Axis. Because their home colony Mahal had been converted into a weapon, Cima and her men were left stranded and homeless.

The OVA will be focus on when Kujaku Nijou first entering group, which occurs one year before the main anime begins.