One day, a girl named Ao Gennai receives a package containing a small robot girl named Gourai. Revealing herself to be a Frame Arm Girl installed with an artificial intelligence, Gourai explains how she was sent to Ao to gather data on emotions. Two more F.A. Girls named Stylet and Baselord soon appear, with Stylet challenging Gourai to a Sessions Battle. Although Stylet initially gets the upper hand with her flight ability, Gourai manages to use her own skills to win the match.

As Stylet acts strangely stiff whenever Gourai comes close to her, she assumes that some trauma is causing her to be unable to fly. After Gourai tries adminestering some shock therapy by kissing Stylet, Ao discovers that she had accidentally stepped on one of Stylet's parts the previous night. Later, Ao receives a seemingly broken cleaning robot, which ends up recording the F.A. Girls as they talk about Ao's embarrassing secrets. After Baselard breaks the robot to keep it quiet, she faces Gourai in a battle to pay Ao back, but loses due to the dust from the cleaning robot.

Base decides to follow Ao to school, prompting Gourai and Stylet to chase after her. Joined by Ao's model-kit obsessed friend, Bukiko Kotobuki, the girls track down Baselard as she starts stealing shiny things from the school. Later, two more F.A. girls known as the Materia sisters arrive and challenge Gourai and Stylet to a battle. As the Materia sisters prove overwhelming even without any armor, Ao gives Gourai a weapon she received from Bukiko, which successfully manages to defeat the sisters thanks to Stylet's support.

Another F.A. Girl named Jinrai comes to Ao's place to battle against Gourai. After Gourai beats her once, Jinrai proposes a sumo match, only to lose that as well. Later, the girls are given their own miniature rooms to decorate. As each of the girls work hard to make their own personal rooms, the Materia sisters use almost all of Ao's savings for their own dollhouse room.

Architect, an F.A. Girl without a physical body, intrudes on Gourai and Jinrai's battle, attacking with clones and pre-programmed subroutines that adapt to the situation. After Gourai and Jinrai manage to win the battle, Archiect experiences an error in her programming, which Gourai manages to fix with her act of friendship. Afterwards, Architect receives a physical body and is delivered to Ao's place. Later, as the cleaning robot is fixed and given the name Sleipni-taro, the F.A. Girls hold a race to buy some vinegar for Ao, with each team facing their own troubles except for Architect.

Ao prepares to go to a fireworks festival but is met with opposition from Jinrai, who believes she shouldn't wear underwear under her kimono. Although the resulting commotion leads Ao to miss the festival, she gets to watch them on the roof with the F.A. Girls. Later, as Ao attempts to finish her summer homework at the last minute, the F.A. Girls are tasked with fetching her notebook from school at night, providing Baselord and the Materia Sisters with an opportunity to scare them by pretending to be ghosts. However, the girls soon become the target of a haunted pair of nippers, which manages to fulfil its goal by snipping a leftover fragment off of Gourai's armor.

While the F.A. Girls play a game of hide-and-seek, Hresvelgr, the self-proclaimed "strongest F.A. Girl", arrives to face Gourai in a battle, managing to completely defeat her. As Gourai feels frustrated over her loss, Ao asks Bukiko about how F.A. Girls are made, helping Gourai to better understand herself and aim to become stronger. After Ao sends in a report, Factory Advance sends her boxloads of new parts.

After a successful test of Gourai's new parts, the F.A. Girls hold a pep rally for Gourai in preparation for a rematch against Hresvelgr. Later, as Autumn rolls in, Ao takes Gourai to the park where she used to go as a kid. There, they come across a girl named Guriko, who leads them to a time capsule Ao had buried containing some mementos, including the Guriko doll she used to have.

Ao ends up catching a cold, prompting the F.A. Girls to go to extreme lengths to figure out how to treat her. When their various methods only make things worse, Gourai learns to consider Ao's feelings and ask her how best to care for her. While resting from her cold, Ao has a dream in which Gourai and the other F.A. Girls are all regular human girls who go to school with her.

Ao holds a hot pot party, but the F.A. Girls can't agree on what kind of hot pot to have. Upon having her hot pot, Ao inadvertently breaks one of the Session Bases used for battles after mistaking it for a hot pot stand. Just then, Hresvelger shows up to challenge Gourai to another battle, revealing that all the F.A. Girls will be recalled to Factory Advance should Gourai lose. Angered by Hresvelgr's treatment of Ao, Gourai launches a powerful attack to clash against hers, resulting in a power cut that forces the match into a draw.

Ao tries teaching Hresvelgr about emotions. Gourai becomes worried about Ao, and later they blow off some steam at a bath.

Gourai won't give up on Hresvelgr, and continues her battle with the help of the other Frame Arms Girls! Later, Gourai realizes what matters the most: friendship.