Commonly known as "Apollo-kun." Other characters call him by various nicknames such as "Horn Head," "Justice-dono," and "Foppish Pipsqueak." His hair is deep brown. His trademark is two spikes of bangs that point up like horns. Depending on his reaction, these two spikes may droop. Even in-game, he is often teased for this distinctive hairstyle, but he seems to be particular about it, fixing it on the spot if it gets messy. Additionally, the ends of his eyebrows are split into two. His clothing is characterized by a burning crimson suit color. He always has his shirt sleeves rolled up and wears a "Bracelet" on his left wrist as an accessory. He does not wear a suit jacket. Unlike Phoenix, he is a hot-blooded youth with a somewhat impulsive yet serious personality. During investigations, he shows excellent insight and a calm demeanor. His catchphrase is "I'm fine!" which once led Phoenix to mistakenly call him "Mr. Fine" when they first met. It was revealed in Ace Attorney 5 that this catchphrase was a "password" between him and his best friend, Clay Terran. Even after the fourth game, he occasionally uses these words to psych himself up or to encourage his clients. He apparently has a loud voice; Athena Cykes says his shout of "I'm fine!" "resonates in the heart and ears." Compared to his somewhat unreliable and flustered days in the fourth game, he shows growth as a lawyer in the fifth game, giving advice as a senior to the rookie lawyer Athena Cykes. In the sixth game, he plays an active role in Japan while Phoenix is away. On the other hand, he is still treated as a handyman by Trucy and is often teased by the Wright father-daughter duo. He also seems to be dense regarding romance; although Athena's best friend Juniper Woods has feelings for him, Apollo remains completely oblivious. Like Phoenix, he has a fear of heights. He is also a poor swimmer.

26 years old. The defense attorney Kristoph Gavin is his older brother. While serving as a prosecutor, he is also the leader (vocalist and guitarist) of the popular rock band "The Gavinners," formed by members of the police force. He is a genius who obtained his prosecutor credentials in the United States at the young age of 17, and his music career saw million-selling hits right from his debut. Songs he is known to have composed include "Love Love Guilty," "13 Years' Imprisonment for Love," and "The Guitar's Serenade" (the melodies and lyrics for these three are known). Others include "Love is Atroquinine," "My Boyfriend is a Prosecution Witness," and "Pardon for Love: Settlement Version." His song titles feature the word "Love" excessively. Incidentally, his album title is "I'm Gonna Arrest You." Surely there were better names than that. First person: I (soft, polite) / I (casual, rare). Second person: you (soft/polite). His ways of addressing major characters are: Apollo Justice -> "Herr Forehead" (rarely "Apollo Justice") Trucy Wright -> "Fraulein" Phoenix Wright -> "Herr Wright" Athena Cykes -> "Fraulein" Ema Skye -> "Detective" (though Klavier is actually one year younger than Ema).

A "prosecutor" who is also a prisoner serving time for murder. Because of this, he wears handcuffs on both wrists. Due to this contradictory title and the frequent trouble he causes in court, he is known as the "Twisted Samurai" (a play on his name, Yugami, meaning distortion). In addition to the usual "Objection!", he shouts "Silence!" He has the appearance of a samurai, with long black hair tied back and a streak of silver, and speaks in a style reminiscent of period dramas. Due to the dark circles around his eyes and his overall aura, he looks somewhat older, but at 29, he is younger than Phoenix Wright. He keeps a hawk named "Taka," who is active in various ways even in the courtroom. He seems to like birds in general, and his favorite animal at the aquarium is the penguin. However, his favorite is clearly the hawk. He addresses Apollo Justice as "Justice-dono," Athena Cykes as "Cykes-dono," and Phoenix Wright as "Wright-dono" (occasionally "Old Man"). He calls Chief Prosecutor Miles Edgeworth "Master Edgeworth" and appears to respect him as a fellow prosecutor. Also, though they don't talk about it much, he and Athena seem to be old acquaintances. On one occasion, when Phoenix was pushing a theory based mostly on speculation that was obvious even to the Judge, Simon snapped, "Get a grip on reality! You're 34 years old this year!" This hit Phoenix so hard that he screamed "Gyaaaaa!" in shock and had to be comforted by Athena. When he gets serious, he performs the feat of breaking his handcuff chains. He uses a blindingly fast "hand-sword" draw to slash the air in front of the defense or the witness, sometimes even cutting off a lock of hair. He attempts this even while bound by handcuffs, though the chains sometimes get in the way. In this state, he corners his opponents further, and the only one who can stop him is the supervising detective, Bobby Fulbright. The method of stopping him involves an electric current delivered through a device built into the handcuffs. His damage motion includes the shock from the electricity, and when countered by a lawyer, he takes damage with a samurai-like slashing effect and clutches his wound. Incidentally, the hardness of his handcuffs is reinforced multiple times throughout the story, but he eventually breaks the chains anyway. He is a man of incredible physical strength.