In the year 1965, a young girl takes a momentous step by using the Hell Correspondence to reach out to Ai Enma, the enigmatic Hell Girl. This process allows individuals, fueled by their grievances, to send those they harbor animosity towards straight to Hell, but at a grave cost: the sender's soul will be condemned to the same fate upon their demise. In a fit of anger, the teen dispatches her tormentor to Hell, but soon finds herself engulfed in regret. Fast forward to 2019, this same girl, now aged and gravely ill, recounts her harrowing tale to her son, Kudo Jin, a journalist who decides to publish her story once she passes away.
Within this narrative, we follow high school student Ichikawa Miho, portrayed by Nana Mori, who experiences a traumatic event at a concert by the radiant musician Maki, played by [Maki Nishiyama]. During this event, Miho falls victim to a lewd encounter, but is rescued by fellow concert-goer Nanjo Haruka, brought to life by Nimura Sawa, who is infatuated with Maki. Their bond deepens, leading them to another concert featuring Mikuriya Sanae, a rising pop star, played by Mina Ōba. However, the evening takes a horrifying turn when a man viciously slashes Sanae's face, leaving her in despair as she grapples with the painful scars of her trauma.
Heartbroken and searching for answers, Sanae stumbles upon Jin's article and, in a moment of desperation, accesses the Hell Correspondence. She types in the name of her assailant, Nagaoka Takuro, embodying the despair and anger she feels. After a chilling vision of Hell, Sanae encounters Ai Enma, who provides her with a straw doll tied with a red thread. The ultimatum is clear: untie the thread, and Takuro will be condemned to Hell, but her soul will follow into the abyss once she dies.
Despite warnings from Jin, who advises Sanae to let go and move forward, she succumbs to the overwhelming pressure from a cruel letter sent by Takuro. Compelled to take action, she unties the thread, resulting in Takuro being dragged to Hell. In the aftermath, Takuro’s mother appears at Sanae's home, begging for forgiveness, only to be met with Sanae's blunt admission of sending her son to Eternal Damnation. With her career on the upswing and Maki now managing her, Sanae's fate takes a turn when Ai reappears to claim her as punishment for the actions taken against Takuro. The tragic twist is compounded by Takuro's mother, who, unable to cope, takes her own life.
The narrative continues with Maki, who, after Sanae's shocking disappearance, auditions a replacement and chooses Haruka, coercing her into substance abuse for personal gain. However, when Ichikawa Miho discovers this troubling development, she attempts to extract the truth from Haruka, only to learn from Jin about Maki's sinister plans for Haruka's future. When Miho and Jin confront Maki's growing dangerousness, their efforts to protect Haruka lead to dire consequences: Jin, after uncovering a plot to sacrifice Haruka, is brutally murdered by Maki, leaving Miho facing an agonizing decision.
Devastated by the loss, Miho resolves to send Maki to Hell, participating in the concert where she pulls the thread of the doll. In a climactic scene, Ai claims Maki, while Miho heroically saves Haruka from a similar fate. Ultimately, the truth about Maki's cruel nature surfaces, resulting in his downfall as his music career crumbles and his associates are apprehended with Kudo’s testimony, ensuring that justice, albeit late, is served. The story concludes on a bittersweet note, as Miho and Haruka reconcile amidst the chaos wrought by vengeance and music that once brought them together.
