Also known as the Hell Girl, Ai is the preternaturally expressionless young girl who comes to deliver vengeance on behalf of those who submit their grievances to HellCorrespondence.com. Though not much is known about this mysterious young maiden, her fate is one of eternally ferrying the damned to Hell, as atonement for some dark deed done... Something tragic surely lies in her past.

Living apart in a world of perpetual twilight, a faceless grandmother, a silent spider and a computer are Ai's only constant companions. When the time comes for vengeance to be delivered, Ai is assisted by three beings under her service, perhaps as mysterious as she. And from time to time, the occasional task at hand or victim will appear to pique her interest...