Initially, the story introduces the general setting of the story - various locations in modern Japan - where certain individuals experience sufferings of various degrees, caused by an antagonist. At one point, they meet a point where they find the pain they experience too much, and they turn to a certain website called Hotline to Hell (地獄通信 Jigoku Tsuushin).
Upon summoning a mysterious girl named Ai Enma to aid them in sending the person's antagonist to Hell after securing a contract, the protagonist is left to decide whether to push through the contract. In most cases, the protagonist seals the contract, dragging the antagonist straight to Hell, while the protagonist receives a seal that reminds the contractor that he or she will be taken to Hell as part of the contract.
In the first season, the story soon follows a journalist named Shibata Hajime, a former blackmailer, and his daughter Tsugumi who shares a strange connection with the Hell Girl as they investigate the truth behind the Hell Girl. In the second season, a mysterious young girl from Hell named Kikuri, who is able to travel freely between Earth and the Twilight Realm where Ai resides, is introduced. Later, the plot centers around Takuma Kurebayashi, a boy who is blamed by his townsfolk for causing disappearances around the town that are in reality caused by the townsfolk using the Hell Correspondence. In the third season, some time after Ai's death, Kikuri returns to recruit Ai's assistants along with a yōkai named Yamawaro, who accepts an old offer from Ai to become her fourth assistant. The story follows Ai's mysterious revival from death and subsequent inhabitation of the body of a young schoolgirl, Yuzuki Mikage.