Like the name of this short series suggests, the manga deals with a crew of cleaners who specialize mostly in taking care of places where people have died. Most of the usually decomposed remains they clean are either of suicides or of elderly people who've died alone. This allows for some very poignant observations about the state of neoliberal society where people are abused by corporations, everyone has to fight with everyone else for the little space and resource allotted to the masses. There are also numerous references to the bust of the bubble economy at the end of the 80s and the decades-long suffering it forced onto people. The majority of the suicides or their neighbors/landlords/etc, for example, are directly hit by it, mostly in the form of extreme loans, or are indirectly suffering because of it, through the way labor and education changed. As expected, the atmosphere in most of the chapters is defined by despair, depression, and alienation.
Structurally, the manga is split into two parts. The first one consists of short stories. Each one lasts for two to four chapters and deals with a different case taken by the company. The stories develop pretty fast and their focus is less on the act of cleaning or the story how the person dies, but on the conversations between the cleaners and their insights into life and death. This is by far the much better part of the manga.
The second part continues to be somewhat episodic but a few overarching plots about a cult and the end of the world start appearing. None of them are given enough time to develop naturally, they are just crammed into the story, develop incredibly fast, and just kind of finish. As such, they leave a lot of questions but not in the way a thoughtfully constructed narrative would. The same can be said about the characters. They are very enigmatic but in the worst way possible. We not only learn almost nothing about them, but also don't witness any growth in them. They are just there, tokens to kind of make the manga supposedly interesting and strange.