I have been watching this series on Animax for a bit now and I have to say that I absolutely love it!
The series is all about wanting revenge and so on. Apparently, if you have a grudge on someone, then you go on to this website that is accessible only at midnight and then enter the person’s name into the text box provided. Then the character of Enma Ai appears and gives you a black straw doll with a red string tied onto it.
The moment you want your revenge, all you have to do is pull that string. But then, there is a catch. “If one person is cursed, two graves are dug!” The girl from hell warns you beforehand, that if she takes your vengeance, then when you die, you will have to go to hell also. Vengeance usually involves that the person whom you hate/bear a grudge on etc gets to go to hell.
So the Girl from Hell goes up to the person and says: “O Pitiful shadow cloaked in darkness. Thy actions cause men pain and suffering. Thy hollow soul drowns in thy sins. Would you like to see what death is like?” and then she whisks off that person to Hell.