One of the classic 2000 Anime series that had quite a following in its time which i only managed to complete its 4 season marathon recently. The series follow after the journey of a mysterious girl named Enma Ai who served on behalf of Hell to send a person directly judged to hell for the begrudged at a price of their soul in afterlife. At first i thought Jigoku Shoujo would be more intense in its horror theme due to its nature but turns out to be still quite mild compared to something like Ghost Hunt. The series could have cranked up the Horror if they want to do as showcased in some episodes but i suppose they want the series to be accessible for teen audience. Jigoku Shoujo spans over 4 seasons though only the first 3 Season can be considered full anime season since it is not easy to get fundings for 26 Anime episodes nowadays.
While Jigoku Shoujo is episodic in its nature, where Enma accepting errands and send people to hell, each of the first 3 Season of the series had overarching theme in relation to Enma's Past, Present and Future which is tied to particular character that had relationship to Enma in some way. The first season had a Journalist whose ancestor had personal bond with Enma when she was human, while second season feature a young boy whose life drastically changed from witnessing Enma in action and finally third season had a middle school girl who is supposed to be Enma's future successor.
While Enma supposed to accept request by people who is wronged by perpetrator who are unable to be judged by law, most of the clients are just as insufferable and no better than the people who wronged them especially the teens. Even Enma's subordinates which are bunch of Youkais had better shred of humanity compared to these clients showing that how depraved human nature could be. Just like Death Note, I think Jigoku Shojo just try to show that supernatural power to kill people does no good in the hands of human as they will end up misusing it anyway.
Despite the animation didn't aged particularly well, Jigoku Shoujo story are still good enough if you want to get some fix of pulpy mild horror anime. There are probably attempts to revive Jigoku Shoujo series but personally i would love to see the ultimate fate of journalist guy from the 1st season.