There is a rumor of a message board called "Jigoku Tsushin", which can only be accessed at midnight. It is said that if a person posts his or her grudge against someone there, the Jigoku Shojo will appear and take the person to Hell.
Jigoku Shojo aka Emma Ai always advices her contacts that in exchange for her sending the target to Hell, the client’s soul will also be taken to Hell after his or her death.