The Devil on G-String's story revolves around Kyōsuke Azai, the adopted son of , a yakuza leader. Kyōsuke works under Gonzō in order to pay off the sum total of a loan taken out by his biological father and the costs of raising Kyōsuke himself under Gonzō's wing. He eventually hopes to reunite with his mother, from whom he was separated many years earlier. At the beginning of the game, a girl named Haru Usami transfers into Kyōsuke's school and introduces herself as "a hero". She initially ignores Kyōsuke, but soon asks him if he knows a person named "Maō". Kyōsuke replies to the peculiar question in the negative, but later that evening, receives a bizarre email from a "Maō". Due to his possible connection to yakuza turf wars, Gonzō instructs Kyōsuke to find and capture the enigmatic figure. The game's expository first chapter ends with "Maō" directly challenging Haru to discover his identity. The second chapter of the game, "Kidnapping Spree", centers on the struggles of the Miwa family to keep their family's orchard, despite both Kyōsuke and "Maō" independently working with a developer who wishes to buy the land. When "Maō" kidnaps the youngest child of the Miwa family and asks for an exorbitant sum as ransom, Kyōsuke helps the eldest, his classmate Tsubaki, obtain the necessary funds via a yakuza loan. Depending on the player's choices, the Miwa family can be saved (granting an ending showing Tsubaki and Kyōsuke cohabitating years later) or forced to accept the developer's offer in order to repay their debt. In all scenarios, "Maō's" demands are met despite the best efforts of the protagonists and Tsubaki's brother is returned safely. It is first strongly suggested in this chapter that "Maō" may in fact be an alter ego of Kyōsuke: his psychiatrist is shown to be acutely interested in memory lapses that coincide with severe headaches and, for the player, with "Maō's" activity. The third chapter of the game, "The Mephistopheles Murders", sees "Maō" take on an accomplice in order to kill people involved with Kanon Azai's skating career. He poses as a radical nationalist to gain the trust of his similarly idealistic accomplice; Haru, Kyōsuke, and Haru's friend Yuki work to save Kanon and her chance at an Olympic quota. After capturing and interrogating the accomplice, the protagonists follow his information into a trap: the entire plot was actually a diversion. "Maō's" actual target was Gonzō, whose enemies he had been arming in order to draw his target out personally. Gonzō had considered this possibility and evades the car bombing which was meant to kill him. It is possible for the player to follow an alternate path in this chapter which sees Kanon and Kyōsuke build a romantic relationship, and portrays her figure skating career in a more detailed manner. In the fourth chapter, "Blind Spot in Negotiations", one of Kyōsuke's classmates takes Mizuha Shiratori and a teacher hostage on the school grounds after hours. Depending on the player's choices, this can be resolved quickly and segue into a romantic subchapter involving Mizuha, or can become a drawn-out affair which eventually leads to "Maō's" final plan. In the latter case, Kyōsuke and his fellow yakuza surround the school while Yuki Tokita, with her extensive knowledge of the criminal mind, negotiates with the captor. Surprisingly, the hostage scenario ends with the revelation that Yuki had enabled the captor to escape at the very beginning of negotiations, and was herself the mastermind behind the event in an attempt to financially ruin Mizuha's father. Furthermore, Yuki is revealed to be Mizuha's neglected half-sister, illuminating her motive. A second, farcical hostage situation occurs when Yuki appears to take Mizuha captive for the second time, but she has no intent to harm her captive. The situation is resolved just as news reaches Kyōsuke that his mother had been killed by a drunk driver. Shortly thereafter, "Maō" succeeds in killing Gonzō, who had apparently to the player discovered that "Maō" was indeed Kyōsuke. Though by all prior indications "Maō" had been a dissociated identity of the protagonist, the fifth chapter, "G Senjō no Maō", reveals it to be Kyōsuke's supposedly dead older brother Kyōhei. he bears a grudge against Haru and Gonzō because Haru's father, a con artist and civil engineer, took advantage of the death of Kyōsuke's little sister to manipulate his family into accepting Haru's father's enormous gambling debt. Ultimately, Kyōsuke's father murdered Haru's father in revenge, and awaits execution. Similarly, Haru's mother was killed by "Maō" years later; thus orphaned, the familial hatred became mutual in a sense. The title of the game is revealed to be taken from a recurring hallucination associated with
post traumatic stress disorder stemming from the moment of Haru's mother's murder: whenever she attempts to play her mother's violin, she sees a demon creep up the instrument's G string. It is revealed that Haru and Kyōsuke met briefly and connected as children. Later in the chapter, Kyōhei initiates an elaborate scheme that drives the entire downtown area into chaos. Kyōhei informs the police that he will demand his army of trained mercenaries and rebellious youths to stand down pending the release of several criminals, including his father. At the end of the event, as Kyōsuke escapes the area, Kyōhei calls him and fakes an emotional suicide. The ruse is quickly discovered and the police engage in a shootout with Kyōhei, apparently ending in his death. In the epilogue, Kyōhei is revealed to have faked his death yet again, and pays Haru a visit at Kyōsuke's home. After a struggle and a chase, Haru nearly murders an unarmed Kyōhei out of rage; Kyōsuke takes the shot instead, in a selfless attempt to spare her from the guilt. When the police question him, rather than attempt to generate sympathy by painting the victim as a brutal killer, Kyōsuke attempts to enrage the investigators with a confession of cruel intent in order to blind them to the facts implicating Haru. He successfully eliminates her association with the crime, but is sentenced to eight years in prison. At his release, he is met by Haru and her daughter, who is revealed to be nearly eight and thus Kyōsuke's. At first, he regrets siring a child who will live with the stigma of a criminal father (like himself, his brother, and Haru), but he is soon overcome by the love in his daughter's eyes, and finally lets go of the past to live for the future. ==Development==