In the world of Karoshi, every person is born into a certain working class. These classes are very hierarchical and there's no way of escaping them, ever. We follow the life of Lucas Rêves, a car mechanic. Car mechanics are the lowest working class and don't get any appreciation for their work. Lucas lives a tough and uneventful life, until on one day, a mysterious man enters his garage. After this figure hits a woman in front of his garage with his car, Lucas gets the chance to make his dream of becoming a surgeon, the highest working class, into reality.