O'Dessa takes place in a bleak, post-apocalyptic future where plazma, a toxic and flammable substance akin to oil, has devastated the environment. The story revolves around a media mogul named Plutonovich, who controls the airwaves from a private island known as "Onderworld." This island serves as a grim arena where dissenters are mercilessly tortured and murdered for the gruesome entertainment of the masses. However, there is a glimmer of hope for the brave—those who survive the deadly competition are celebrated as "The One" and are granted a wish.
The protagonist, O'Dessa, is the seventh generation of the wandering "ramblers." Following the death of her mother, she inherits her father's guitar, setting her on a perilous journey to Satylite City in search of her destiny. Along the way, O'Dessa's beloved guitar is stolen and pawned, leading her on an adventurous quest to reclaim it. During her journey, she crosses paths with Euri Dervish, a musician and sex worker serving under the ruthless Neon Dion, who is Plutonovich's main enforcer.
As fate would have it, O'Dessa and Euri develop a romantic bond and plot their escape to the safer haven of Enid. But their dreams are shattered when Dion catches wind of their plans and threatens both of their lives. In a desperate act of bravery, Euri manages to steal enough money from Dion to buy back O'Dessa's guitar and implores her to leave for Enid without him. In a fit of rage, Dion retaliates by gruesomely cutting off O'Dessa's ring finger as a warning. Trapped in this whirlwind of chaos, O'Dessa and Euri still dream of marrying each other. However, their plans are dashed when Euri insults Plutonovich during a performance, resulting in his abduction to Ontwerworld, where he is forced to dance for his survival.
Determined to save her love, O'Dessa embarks on a dangerous trip to Onderworld. There, she bravely performs before Plutonovich and his entourage, ultimately earning the title of "The One," even though she is left with only one string intact on her guitar. In an effort to reclaim Euri, she uses her wish to bring him back, but the wish comes at a devastating cost—Plutonovich has altered Euri's mind through a procedure that leaves him brain-dead.
In a tragic yet powerful climax, O'Dessa sets her guitar ablaze and destroys Plutonovich's plazma-fueled media empire—an act that claims her life, Euri's life, and Plutonovich's life. Through this ultimate sacrifice, she liberates the masses from his oppressive grasp. As the story concludes, the toxic plazma begins to recede from the landscape, and the citizens pledge to honor O'Dessa by sharing her music and the enduring message of hope she represented.
