* 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. Besides, Ai Enma will not magically appear to give you the black straw doll, which should be the process between clicking 'Submit' and sending your target to hell.]]
* ScrewedByTheNetwork: Animax Latinamerica licensed the second season and was supposed to have a dub...and then the channel rebranded.
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