Companions

Though I can't elaborate much on her feelings for the four of them, I do think a connection can be drawn as to why she bothered saving them from despair to begin with. Putting aside the fact that it would be hard to accomplish her job by herself, Ai can see that they were alone. They suffered greatly before death and ended up by themselves. All of them were isolated from their surroundings, whether they had been outright rejected, didn't know kindness or were left behind. She knows very well what it is like to be and feel alone. Picking up four wandering souls out of compassion could show not only that Ai feels bad for those who are alone, but also that she hates feeling lonely herself.
Each of Ai's companions could quite possibly represent different aspects of her own feelings and story as well in the following ways:
WANYUUDO (black straw doll) was once a carriage for a princess and her family. While being pursued, he goes over a cliff in flames with the princess in it; resulting in all of their deaths. Ever since, his spirit haunted the mountain path where he slipped in the form of a giant flaming head on a wheel. He purposely scared all the people who passed. Ai, who happens to be traveling through the mountain, is not startled by him at all. Wanyuudo is intrigued by her lack of reaction and chooses to follow her and see what she does. Because Ai is always walking everywhere, he ultimately decides to become her "feet" by transforming into a flaming carriage for her to ride in instead.
Wanyuudo's story represents the despair and rage that Ai feels in her heart. Her killing everyone in the village can be drawn to Wanyuudo's weakness killing the princess in flames. Though she "chooses" to do it unlike it being an accident for him, they both supposedly lost the people they cared about. Wanyuudo's despair and rage is displayed by his spirit taking the form of a giant flaming wheel terrorizing innocent people who walked by. This can be paralleled to Ai's own rage when she remembers the past and tries to kill Hajime and Tsugumi, who really had nothing to do with her despair either.

Ichimokuren's story represents Ai's current state of being. Despite not wanting to hurt others or send innocent people to Hell, she has no choice. Her "master" is the boss of Hell, and therefore she has to continue her job even if it goes against her personal values or feelings. I'm sure she feels just as much frustration as he did when he had no say in what he cut down.

Hone Onna's story represents Sentarou's betrayal. Like Hone Onna, Ai was betrayed by the guy that she loved and trusted. Instead of being tossed into a river, she was buried alive. Either way, she was ultimately "disposed" of, even if Sentarou didn't actually want to hurt her. Ai "rises" from the dead as a result of her restless soul in a similar fashion to Hone Onna. They both carry the grief of being betrayed and killed even though they did nothing wrong.

Lastly, Yamawaro's story represents Ai being outright rejected by everyone for being "different." Though Ai never was responsible for the things she was accused of, people were afraid of her and therefore ultimately wanted nothing to do with her. Though the situation made her sad, she really didn't have memory of it ever being better. Despite having Sentarou, she still had to spend a lot of time living alone in the forest, hiding from others.
b a c k . c l e a r . f o r w a r d Heaven's a Lie and its contents are © Samantha, however Ai and Jigoku Shoujo are © Aniplex, Studio Deen and other rightful owners. Heaven's a Lie is a part of AFTER-DEATH.ORG.