The main protagonist of the Great Ace Attorney series and the primary playable character, Ryunosuke is the ancestor of Phoenix Wright and like his descendant, aspires to be a successful lawyer. However, his first appearance in the courtroom was in defense of himself, and he only seriously began to consider a career in law when his best friend, law student Kazuma Asogi, perished aboard the SS Burya on the way to a study tour. Now Ryunosuke has taken Kazuma's place in London, and intends to carry out his friend's dream in his honor.
The judicial assistant of Ryunosuke, Susato has always played a supporting role in his trials. While she initially doubted Ryunosuke's abilities in contrast to her admiration of Kazuma, Susato has grown to trust and respect Ryunosuke, and the two have developed a close bond over the course of their trials in London. However, Susato had no choice but to return to Japan when she received a telegram notifying her that her father and mentor, Professor Yujin Mikotoba, has fallen ill. Thus, she begins the game in Japan, and while she intends to make a trip back to London, she first must assist her old friend in court.
The best friend of Ryunosuke, Kazuma Asogi was a law student who exhibited great skill in his craft. He was selected for a study tour to London for this reason, during which he intended to learn from the advanced British judicial system in order to improve the judicial system in Japan. However, this dream was cut short when he died aboard the ship that would have taken him to London, leaving his best friend who he had secretly accompany him to take his place. Kazuma also alluded to something he had to do in London, though Ryunosuke was unable to find out what that was before his death.
A famous detective who works out of his own office on Baker Street, Herlock Sholmes has become a trusted ally to Ryunosuke and Susato during their time in London, and has even provided them a place to stay above his own lodgings. His work as a private investigator allows him to freely investigate any case that interests him, much to the ire of the strictly structured Scotland Yard. He often assists Ryunosuke in his own investigations as a result, though his quick deductions aren't always accurate.
A young girl who lives with Herlock Sholmes, and has become acquainted with Ryunosuke and Susato as a result. Iris acts as Sholmes' assistant, as despite her age, she exhibits extraordinary intelligence. Like Sholmes, she has a knack for deductions and unique inventions, and she also writes about the many cases that he solves (though she tends to embellish). Her stories have become quite famous in Britain and have even captured an international audience, making the name Herlock Sholmes widely known as a result.
Barok van Zieks
A successful prosecutor and rival to Ryunosuke in court, Barok van Zieks has been feared ever since his career began as "the Reaper." This reputation developed due to the mysterious death of defendants that he ultimately wasn't able to convict, leading to a common belief that the Reaper's judgment is inescapable. His general unfriendliness aside, Barok van Zieks also appears to harbor a deep resentment for the Japanese, a prejudice which he takes out on Ryunosuke. It is perhaps due to this resentment that Ryunosuke has yet to face any other prosecutor in court.
A prolific detective at Scotland Yard, Inspector Gregson is trusted by both Barok van Zieks and Mael Stronghart with important investigations. He has a strong dislike of Herlock Sholmes due to the hold his stories have had on his reputation, though he treats the actual writer of those stories, Iris Wilson, with an exaggerated kindness. He receives a royalty in return for his "appearances" in these stories, and has noted that while they have given him some unwanted fame, he also received a promotion due to his portrayal. Gregson can always be found with some fish and chips in hand.
The Lord Chief Justice of London, Mael Stronghart granted Ryunosuke permission to act as a lawyer in Britain following his successful first trial. However, that permission was taken away when it was discovered that perjury was committed in that very trial, and a not guilty verdict was falsely handed down due in part to Ryunosuke's efforts. Though he is respected due to his high position, Stronghart always appears to be overly concerned with time, and is constantly looking at his pocket watch as a result, even during conversations with others.