Jigoku Shoujo, known in English speaking countries as Hell Girl, is a series originally consisting of an anime, which currently has three seasons, with a fourth upcoming season to be released in 14th July 2017. It has also been adapted later on into a manga series, a live-action television series which has finished airing, and a few games. Each of these adaptations follow different storylines which are not canon with the others, though they have core similarities to the anime.
The story revolves around a girl named Ai Enma. Her existence is an urban legend known only by few, and most of these people know her instead by the name Jigoku Shoujo (Hell Girl). She is known for the service that she is rumored to provide, which is to carry out grudges on behalf of the clients who request her service by sending the person the client holds a grudge against to hell.
The means of requesting her service has changed with time, with the latest means being a website known as the Jigoku Tsūshin (Hotline to Hell). Knowledge of the website's existence is an urban legend known only by few as well. It is only accessible exactly at midnight, and can usually only be seen by those who bear significantly powerful grudges. This website can be used by someone to enter and send the name of the person they have a grudge against and send it.
After a request has been sent to Ai, she has her servants (or companions) investigate the client and/or the would-be victim discreetly, sometimes joining in herself in the investigation as well. The investigation is often done by supernatural means, and for various reasons, through which Ai decides whether or not to give her service to a client. If she accepts the client's request, she will approach the client and hand them a straw doll. She will then explain the terms of her service, which states that if the client wishes to continue, he or she must pull the red string tied around the neck of the straw doll. After doing so, Ai will take the person who the client sent the name of immediately to hell. However, by pulling the red string, the client agrees to the condition of her service, which states that he or she will also be sent to hell, but only after his or her natural life comes to an end.
The story of the series has a recurring theme of injustice, hatred, suffering, and revenge. Elements like violence, harsh language, trickery, blackmail, animal cruelty, torture, insanity, twisted and complex human emotions, and such are common elements of the series.