Each game has its own individual plot but the characters and their relationships remain intertwined throughout the series.
In the first three games, the main playable character is Phoenix Wright. He is a rookie lawyer fresh out of law school in the first game, taking a position at Fey & Co. Law Offices run by Mia Fey, a defense attorney that helped to acquit Wright of murder several years prior to the events of the first game. When Mia is murdered, Wright takes over the offices with the assistance of Maya Fey, Mia's younger sister, and renames the office "Wright & Co. Law Offices". The Fey family have the ability to channel spirits, which sometimes allows Maya or her much younger cousin Pearl Fey to channel Mia's spirit to help Wright in court. Wright develops a rivalry with prosecuting attorney Miles Edgeworth as they oppose each other in court. Wright's victories over Edgeworth (along with Wright's victory over prosecutor Manfred Von Karma) introduces a third prosecutor to combat Phoenix in court, Franziska von Karma, who sees Edgeworth as a younger brother (despite actually being several years younger than he is). She is determined to succeed where her father and Edgeworth failed by winning against Phoenix in court. In the third game, Phoenix's main rival in court is Godot, a mysterious prosecutor who holds some kind of grudge against him. Also more info related to Phoenix, Mia and other members of the Fey family is unveiled, intertwining with the events from the previous games until the last case, which closes the Phoenix Wright chapters of the Ace Attorney series.
The fourth game shifts seven years after the first three games. Phoenix, having been disbarred for unknowingly using falsified evidence, has become a piano player, adopted a young magician named Trucy, and has transformed the office to the "Wright Talent Agency". When he is accused of murder, he spies the upcoming and talented defense attorney Apollo Justice with his "Chords of Steel" and has him defend him as well as hiring him, forcing the office to be renamed "Wright Anything Agency". While Apollo and Trucy handle cases, Phoenix still works with ties to the justice system to implement changes that will help improve the courts, including the introduction of a "Jurist System" that leaves the decision of guilt or innocence to a six-panel jury, while investigating the remaining mysteries involving his last case seven years before.
Set between Trials and Tribulations and Apollo Justice, the interquel series Investigations, features Miles Edgeworth as the main character. While and after returning from a trip to Europe, Miles is thrown in a series of incidents tied to a mysterious smuggling ring also involved in the creation and distribution of counterfeit money and art pieces. The game also features important characters like Franziska who is working with the interpol to break down the ring and detective Dick Gumshoe. Key characters exclusive to this game include Kay Faraday, who claims to be the successor of the legendary thief Yatagarasu, and Shi-Long Lang, an interpol agent who for some reason despises prosecutors. One of the cases is a flashback featuring Miles and Franziska's mentor Manfred Von Karma and depicting Miles' first encounter with Kay and Gumshoe.