Akinari is a dying young man who writes to ease his mind. Through the Main Character's interaction with Akinari, he helps him in understanding his purpose in life and helps him to overcome his grief of his disease. In Persona 4, Kanji Tatsumi reveals that Akinari's book was indeed published. Akinari is the social link for the Sun Arcana.
Jin is Takaya's faithful right-hand man, acting as his tactical adviser and the webmaster of "Revenge Request." He uses grenades and bombs in battle and is also a skilled computer hacker. Jin appears very eager to be rid of SEES, since he believes that they are hypocrites who don't appreciate their own power. However, he is rational enough to limit Takaya's actions when necessary. Whenever Takaya takes a reckless approach, Jin is there to hold him back and remind him of what they are truly there for. Jin is a zealot with strong belief in Takaya's goals. He is fiercely loyal to Takaya for "showing him out of darkness" and helping him through the Kirijo Group's experiments. In spite of this, he often inadvertently helps SEES by revealing important information. It is Jin who informs the Main Character about the truth behind Strega, their involvement in the coming of Nyx, and Shuji Ikutuski's real allegiance. At the end of the game, Jin sacrifices himself to buy S.E.E.S time by setting off a grenade that holds back a hoarde of Shadows in Tartarus.
Takeharu Kirijo is Mitsuru's father and the president of the Kirijo Group. He is the son of Kouetsu Kirijo, the corporation's former president, who began a series of experiments on Shadows seeking to harness their power. He rejects the ideology of his father, who believed death was a form of deliverance. Shuji Ikutsuki murders Takeharu on the roof of Tartarus, saying he did not understand his father's vision.
A confident athlete. He has an injured knee, but he asks the Main Character to keep it a secret from his teammates. His arcana is the Chariot.
Originally, Ryoji shows up as a new transfer student, and becomes fast friends with Junpei and the rest of the group. His cheerful and reckless dating attitude is also subject of much talk, even going as far as asking Yukari as well as Mitsuru on a date upon first sight. Aigis remained extremely cautious of him, however, constantly referring to him as "dangerous." His true identity is "Nyx Avatar" as well as the Appriser and harbringer of "Death" and Nyx. He is also the older version of Pharos. The fun doesn't last long though, as a battle with Aigis on Moonlight Bridge finally awakens his memories of his true purpose. When the group gets there, they find a damaged Aigis, and an unconscious Ryoji. After he recovers, he tells them everything he knew, and expressed that he is tormented by the fact of who and what he is more than anyone. He gives the group a choice: they can kill him on the spot, and the Dark Hour will vanish, and they will forget everything, and return to their normal lives, or they can let him live. Either way, according to him, it is inevitable that the world will end at the hands of Nyx; only by choosing to kill them, will their world end in a somewhat "painless" fashion. Depending on the choice the player makes, they can either kill or let Ryoji live, each resulting in a different ending. During the discussion with the main character, he shows that he is also Thanatos, the Ultimate Persona of the Death Arcana.