"The series follows a young girl named Rakka, a newly arrived haibane (an angelic-looking being), and other characters in the city of Glie (guri), a walled city with one entrance where no one is allowed to leave. (See http://en.wikipedia.org/wiki/Haibane_Renmei for more.)" -Manga Updates

Chapter 0, "Charcoal Feather Federation" was the original installment of the Haibane Renmei series, though it is mostly unrelated to the following chapters.