I think posted my thoughts on the above questions in either one of the existing
Jigoku Shoujo threads.
In my opinion, the
jigoku tsuushin is eternal. It's been there since the beginning of time, as humans perceive it. It represents a very specific human sin, the desire for revenge. The
tsuushin will exist as long as humans continue to hate.
I also strongly suspect that there had been previous Hell Girls before Enma Ai. Just as the
tsuushin represents sin, Ai is the anthropomorphication of revenge. Perhaps the personality of each Hell Girl represents a different point-of-view on bloody grudges?
My inspiration for the above theory comes from
The Endless, created by Neil Gaiman for the
Sandman series.
I was particularly struck by the "trinity" of the Grandmother (the crone, the spinner), Hell Spider (the "woman", the weaver) and Enma Ai (the maiden, she who cuts the cloth of destiny). Yup, I'm referring to the
Three Fates of Greek and Nordic mythology, who also happen to appear quite frequently in the
Sandman series, often with tragic results.
If the third season turns out to be something like the above, I would be
extremely impressed. But I'm not holding my breath, heh.