JOKER is an alias used by Tatsuya Sudou during the beginning of Persona 2: Eternal Punishment. JOKER can be reached by someone calling themselves on their cell phone. According to the rumor, he will kill anyone you ask. Following the events of Persona 2: Innocent Sin, the events are erased from everyones mind and Sudou is committed to a sanitarium. Nyarlathotep returns Sudou's memories, and Sudou escapes as JOKER to murder people by spreading rumors.
Realizing how dangerous he is, Tatsuzou Sudou, Sudou's father, attempts to kill him using members of the Taiwanese Mafia. This fails and all of them are slaughtered. Sudou escapes from the sanitarium for good and lures Maya Amano and Jun Kurosu to the Sky Museum, which he proceeds to set on fire. Sudou is still loyal to JOKER, so he attempts to get Jun to remember the events of Persona 2: Innocent Sin. This fails, and Jun pushes Sudou into the flaming building's collapsed roof. Sudou emerges alive, but scarred and with only one eye. He is killed by Tatsuya Suou.