* AnimeFirst: The anime and manga began releasing almost simultaneously, but the former is the original and the latter the adaptation (anime has a longer lead time than manga). The manga's quite different, and lacks Hajime and Tsugumi except in omakes.
* ContractualImmortality: [[spoiler:Ai]] was dead by the end of season 2 but they wanted a third so...
* {{Defictionalization}}: Someone has actually made a real "Hell Correspondence" website. For those who seek vengeance, the site can be found [[http://jigokutsushin.co.nr/ here]].
** [[spoiler: By the way, it doesn't work. Your target will not ''actually'' go to hell, so you need not fear having a certain black mark put on your neck setting ''you'' on the path to hell.]]
* ScrewedByTheNetwork: Animax Latinamerica licensed the second season and was supposed to have a dub...and then the channel rebranded.
----