In the midst of Shouwa era Japan, greed runs rampant through the bustling cities and communities of the nation. King of Hell Enma Daiou summons an envoy into his office in the form of a small boy named Kurayami Santa. Through Enma's debriefing, Santa learns that the amount of greed and selfish behavior produced by humans will soon create an enormous wave of souls entering into Hell simultaneously, which would be catastrophic for Hell itself.

Santa is given one mission: do something about it. With neither guidelines nor rules, Santa is tasked to handle the situation as he sees fit. In the human world, a rampaging thunderstorm strikes a nearby cemetery with a bolt of lightning, and the envoy of Hell appears.

Teleported into the human world, Santa quickly realizes that humans are just as wicked as Enma had described. Without upsetting the balance between light and dark, Santa begins his quest to complete the mission from Hell and restore order to the human world.

Morimura Tomomi is a housewife scorned by her husband and two sons, and yet she continues to protect the family. On her 46th birthday, she leaves home in disgust and embarks on a 1,200 km journey. It is Tomomi’s first time driving onto the highway and she speeds along to the west. On the road, she encounters a series of traumatising episodes. She detects her husband’s affair, is faced with a truck driver who mistakes her for a prostitute housewife, and finally her car gets stolen. While Tomomi is at a loss, a good-looking young man and an elderly person give her a ride, and she arrives in Nagasaki. As she meets various people in this town which was once transformed into a wasteland because of the atomic bomb, she becomes aware of a “wilderness” within her and starts to explore the path to rebirth