"A masked figure rumored to grant one's dreams. Why he does this, and who he is, is a complete mystery."
—Persona 2: Innocent Sin introduction
In Sumaru City, there are rumors that a mysterious man known as the Joker can answer wishes submitted to him by a phone call. However, if the person who summons them doesn't have a wish on their hearts, Joker instead claims the dreams of his victims, and reduces them to shadows of their former selves. The Joker tends to leave behind flowers as a reminder to his victims of the sins they've committed.
The Joker is also the leader of the Masked Circle and is gathering the Ideal Energy from his victims' dreams to awaken the ancient city of Xibalba, in accordance with the prophecies in In Lak'ech.
It was later revealed that the Joker's true identity is Jun Kurosu, Maya's childhood friend, and the Masked Circle used to be a Featherman-roleplaying group consisting of Maya, Tatsuya, Eikichi and Ginko. The Joker is merely a form Jun took to claim punishment from those he deemed guilty for the fire that nearly killed Maya Amano years ago, supposedly being his childhood friend Tatsuya Suou. In reality, the person he believed was the arsonist was a false memory created by Nyarlathotep, and the real arsonist was Tatsuya Sudou, whom Suou defended against by awakening his Persona. Nyarlathotep, as seen during the game's events, took the form of his father and manipulated Jun into doing his bidding.
When the party finally reaches him at the Caracol, the Fuhrer, his troops and the Shadow Selves of Tatsuya, Lisa and Eikichi can be seen alongside Joker, who collects the five crystal skulls to unleash Xibalba. Maya tells him that dreams shall not be given but attained via one's own power, yet Joker rebukes her as having an overly sugarcoated view, with the Furher agreeing with him, that humanity only wants a ruler to think for them, and Joker announces that he will guide humanity to a golden age. However, when Xibalba emerges from the ground, the Joker displays signs of remorse for unleashing Xibalba and suddenly recollecting that he's actually Jun. He also had a feeling that Tatsuya Suou might not be the arsonist who traumatized Maya. Queen Aquarius sacrifices herself to protect Joker/Jun from one of the Longinus Knights, revealing herself to be actually Jun's mother. Joker tries to fight back with his Persona, Nyarlathotep, but to no avail, and the Furher flees alongside his troops. He then orders Shadow Lisa, Shadow Eikichi and Shadow Tatsuya to leave, before displaying further signs of fully recollecting his true identity. Despite this, Nyarlathotep reaches out to him and tells him that he is Joker and Tatsuya Suou is the arsonist.
After Joker is defeated, he is possessed by Nyarlathotep and is forcibly transformed into Angel Joker. Should the party defeat the Angel Joker as well, he will be freed from Nyarlathotep's manipulations and revert back instantly into Jun Kurosu. Jun will join the party permanently in place of Yukino Mayuzumi afterwards.
An A-Rank BattleNet opponent who can supposedly grant any wish. He has a collection of rare demons, and is said to act unpredictable and have a lot of style. He gives a Scylla after 7 defeats, Clotho at 17 defeats, and Lachesis at 27.
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