The story follows Iruma Suzuki, a 14-year-old human boy, who is sold to a demon by his parents. The demon, known as Sullivan, takes Iruma to the Demon World and officially adopts him as his grandson. He enrolls Iruma in the Babyls School for Demons where he is the headmaster and where Iruma quickly befriends the demons Alice Asmodeus and Clara Valac. However, Sullivan tells Iruma to never reveal that he is human since he will be eaten if anyone finds out. Iruma then vows to blend in during his time in the demon world, although he only stands out because of all the situations and adventures that arise.

Shamisen is a traditional Japanese musical instrument that looks similar to a guitar. Teenager Sawamura Setsu's grandfather who raised him and his older brother Wakana, recently passed away. His grandfather was one of the greatest Shamisen players and the two siblings grew up listening to him play and learning to play the instrument. Since their grandfather's death, Setsu dropped out of high school, moved to Tokyo and has been drifting, not knowing what to do besides play his Shamisen. That's when his successful and rich mother, Umeko, storms into his life and tries to shape Setsu up. She enrolls him back into high school, but little does Setsu know that he is about to rediscover his passion for Shamisen. (Source: MU, edited)

The Republic of San Magnolia. For a long time, this country has been besieged by its neighbor, the Giadian Empire, which created a series of unmanned drones called the Legion. After years of painstaking research, the Republic finally developed autonomous drones of their own, turning the one-sided struggle into a war without casualties—or at least, that's what the government claims. In truth, there is no such thing as a bloodless war. Beyond the fortified walls protecting the eighty-five Republic territories lies the "nonexistent" Eighty-Sixth Sector. The young men and women of this forsaken land are branded the Eighty-Six and, stripped of their humanity, pilot the "unmanned" weapons into battle... Shinn directs the actions of a detachment of young Eighty-Sixers while on the battlefield. Lena is a "handler" who commands the detachment from the remote rear with the help of special communication. The farewell story of the severe and sad struggle of these two begins! (Source: MU, Yen Press; edited)

The anime centers on Manatsu, who moves from her small island birthplace to a city and starts middle school. On the day she moves she meets a mermaid girl named Laura who is looking for the "legendary warriors," the Precures. Laura's hometown, the mermaid country of Grand Ocean, has been attacked by the "procrastination witch," who has stolen the country's "motivation power." (Source: ANN)