Hell Girl

Hell Girl (地獄少女 Jigoku Shōjo), also known as Jigoku Shōjo: Girl from Hell, is an anime series produced by Aniplex and Studio Deen. It focuses on the existence of a supernatural system that allows people to take revenge by having other people sent to Hell via the services of the mysterious titular character and her assistants who implement this system. Revenge, injustice, hatred, and the nature of human emotions are common themes throughout the series.

Plot
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.

Characters
Ai Enma (閻魔 あい Enma Ai)
 * Voiced by: Mamiko Noto
 * The main protagonist of the series, who is arguably an anti-heroine as well. With long, straight black layered hair with a fringe, ruby-red eyes and pale skin, she is a spiritual entity with a tragic past, who lives in a place frozen in time as it basks in eternal sunset, along with her grandmother.
 * She exacts the revenge of people as the Hell Girl, utilizing the Hell Correspondence to receive the names of people that are to be sent to Hell for the sufferings of others.

Hajime Shibata (柴田 一 Shibata Hajime)
 * Voiced by: Yuji Ueda
 * A former journalist who earns money by blackmailing celebrities with evidence of their scandals. He began to investigate rumors about the Hell Correspondence website merely out of curiosity, but becomes more heavily involved once he realizes that it is more than just a rumor and people are actually being dragged into the pits of Hell.

Tsugumi Shibata (柴田 つぐみ Shibata Tsugumi)
 * Voiced by: Nana Mizuki
 * Hajime's daughter. She seems to have a mysterious connection with Ai Enma, which allows her to see anything significant that Ai sees. Using this ability, she and her father track down Ai's clients in an attempt to stop them from damning one another.

Other Sources
Review of Jigoku Shoujo at Anime Academy