Innocent Sin begins with Tatsuya and Lisa being lured by Eikichi to where his band is rehearsing in an effort to get Tatsuya to join his band. During the ensuing argument, their Personas reveal themselves and Philemon contacts them, warning them that rumors are becoming reality in Sumaru. The group then act out a game where a figure called the Joker is summoned to grant a wish. When Eikichi and his band do this, the Joker is summoned, then drains all the players but Lisa of their "Ideal Energy" (the essence of hopes and dreams) using a crystal skull. The Joker then attacks Tatsuya, Lisa and Eikichi, accusing them of some unspecified "sin", but leaves when they cannot remember that sin. As the group attempt to learn the Joker's identity, they are joined by Maya and Yukino, the latter of whom is able to explain their Persona abilities. They are eventually brought into conflict with the executives of the Masked Circle, a cult led by the Joker who are gathering Ideal Energy using assigned crystal skulls. They are King Leo (Tatsuya Sudou), a deranged man whose eye was burnt out; Prince Taurus (Ginji Sasaki), a record producer who manipulates Lisa's budding girl group for his own ends; and Lady Scorpio (Anna Yoshizaka), a former student at Seven Sisters who is brainwashed by the group. The group are gradually fulfilling the Oracle of Maia, recorded by Akinari Kashihara (Jun's father) under the influence of Nyarlathotep.
