闇に纏いし哀れな影よ。 人を傷つけ貶めて罪に溺れし業の魂 ・・・イッペン　死ンデミル？'

"O miserable shadow clad in darkness! Hurting and disdaining people, a karmic soul drowning in sin... Would you try dying for once?"

Jigoku Shōjo

— Enma Ai.

"At midnight every night, you can access Jigoku Tsūshin online. If you type in the name of someone who you have a grudge against there, Jigoku Shōjo will appear and send that person to hell. Rumors of the site spread among children living in cities. However, no one speaks of one thing, that you must make a contract with the Jigoku Shōjo to carry out revenge against your grudge."

The series is mainly a collection of short stories. Each of them describes the suffering of a different individual caused by one or more antagonists, and the subsequent punishment inflicted on the antagonists with the help of Enma Ai, aka the "Jigoku Shōjo" (Hell Girl).

During each story, the protagonists' dramas are explained in detail from the start of their grudges, through the escalation of their torment until it becomes unbearable and they resort to the "Jigoku Tsūshin"(correspondence with Hell)- a mysterious black colored web site only accessible at midnight. The contents of the site are only a text: "あなたの怨み、晴らします。 (We will take revenge on your behalf.)", a text box where the grudge's object must be written, and a "送信 (Send)" button. Some time after the post, they are visited by Enma Ai, a young red eyed girl wearing a traditional sailor school uniform. She delivers them a black straw doll (In the second season, the doll may also be red or dark blue depending on who turns into it) with a red string tied to its neck, and she tells them that if they want their vengeance to be delivered, they must remove the string from the doll, and their enemies will be immediately taken to Hell. However, a crest shaped mark will appear on the protagonists' chests, always reminding them that after their lives come to an end, they must give compensation by having their own souls also sent to Hell.

Enma Ai doesn't work alone. She lives in a house in an unknown world that is in eternal sunset with her grandmother who orders her around and whose face never appears. Ai also counts on the help of her three assistants. When they are not under her services, they stay in the form of three straw dolls, otherwise they assume the form of Ichimoku Ren, a handsome young man in casual clothes, Hone-Onna, a beautiful woman wearing a kimono and Wanyūdō, an old man wearing a hat and a red scarf. They help her during the event when their victims are confronted with their own sins, prior to the moment when Ai (dressed in traditional kimono with floral patterns) ferries them to hell. Also, the trio helps her investigate the true nature of their cases when something seems suspicious.

In episode 8 of the series, two other recurring characters are introduced: A journalist named Shibata Hajime who is investigating the stories involving the Jigoku Shōjo, and his daughter Tsugumi. After an encounter with Enma Ai, Tsugumi starts to have visions of what Ai sees and thus the two become more and more involved in Ai's matters. The fact is Hajime doesn't agree with Ai's methods; he believes people should solve their problems by other means than resorting to vengeance, and tries to stop those who contracted to the Jigoku Shōjo from sending their grudges to Hell with Tsugumi's help. As the story progresses, Tsugumi begins to question if Ai's ways are as wrong as her father believes, but little do they know about the true reason why their thoughts are connected.

Official site: http://www.ntv.co.jp/jigoku/

Source: Wikipedia