The anime's story begins when Ao opens a package that arrives at her doorstep. Inside the package is Gourai, a Frame Arms Girl: a small robot capable of independent movement. Gourai is a newly-developed prototype: a Frame Arms Girl equipped with an "Artificial Self," an advanced AI that gives her a personality. Ao is the only one that has activated her. Gourai begins to gather both battle data and emotions, starting a day-to-day life with Ao, who knows nothing about Frame Arms Girls.
Summary taken from: MyAnimeList