"The AI no Idenshi - Episode 5" begins with Yuta, a humanoid, struggling with his emotions. He often loses control and gets into fights over trivial matters, leading to frequent visits to the student counseling room. Yuta wonders whether this is just his personality or a flaw in his system.

At the Sudo Novo Medical Clinic, Yuta's mother discusses her husband's insomnia with Dr. Sudo. She suspects her husband is hiding something from her, as she discovered he deposits large sums of money into an unknown account every month. Her husband claims he is donating to a charity run by an old friend.

Dr. Sudo discovers that the memories of Yuta's father were overwritten six years ago through an invasive procedure that does not comply with legally approved treatment methods. The father cannot remember it, as the doctor who performed the procedure likely erased the memories of the operation. Dr. Sudo confronts the responsible doctor, Seto, who admits to altering the father's memories to help him gain control over his life.

Meanwhile, Yuta's mother decides to have Yuta treated for his emotional instability. Dr. Sudo and a medical AI named Jay suggest tuning Yuta's emotional system, thereby changing his personality. Despite her initial hesitation, Yuta's mother agrees to the treatment.

After the treatment, Yuta becomes calmer and more sociable. He is no longer overwhelmed by his emotions and can get along with his classmates. He continues to play the piano, but he notices that his music sounds different.

The episode ends with Dr. Sudo reflecting on how easy it is to alter a humanoid's personality and implant false memories.