Mechanical Arms

Hikaru Amatsuga is a middle school student who lives in Kita-Kagami City; he finds a mechanical lifeform in the shape of an arm named Alma.

The Mecha-Ude user Aki Murasame transfers into Hikaru's class with the intention to secure Alma.

Hikaru and Alma are taken to ARMS HQ, where Hikaru is told that he is not suited to be a Mecha-Ude user and Alma falls under ARMS' protection; multiple incidents occur where Mecha-Udes are forcibly ripped away from their users.

Hikaru was dealing with the fact that he had to still go to school while learning to live with Alma, working as a member of ARMS, and being followed around by Aki.