The Japanese Censorship Collection contains 1,327 marked-up copies of censored monographs and galley proofs for approximately 1,100 titles, mostly from the 1920s and 1930s. They include copies submitted by publishers for examination by censors in the Home Ministry of the Japanese imperial government as well as books lawfully confiscated by the ministry and local authorities for censor review. The practice of censorship were carried out "to protect public order 'annei' and the manners and morals 'fuzoku'" in Japan. To achieve these ends, censors suppressed "kinshi", deleted "sakujo" or revised publications "kaitei" they deemed a threat to social and political stability.

Many of the materials in this collection were banned from publication and distribution. Such decisions are often readily indicated by the censors' comments written directly on copies of the offending books. These marked-up copies from the Home Ministry's library constitute the censor's archive and contain marginal notes, stamps, penciled lines and comments on text, and other signs which reveal then hidden traces of the censorship process. These materials clearly stand out as different and unique from all other existing copies and editions of these titles in Japan, and their research value is extremely high.

The majority of the collection dates to the period between 1923, when the Home Ministry's building in Tokyo burned down in the Great Kanto Earthquake, and 1945, when the imperial Japanese government's surrender marked the end of the World War II. Following Japan's defeat, the ministry's censorship library was seized by the Allied Forces and sent to the Washington Document Center (WDC) in the United States. Afterwards it was transferred to the Library of Congress, along with massive volumes of books and other materials confiscated from such official institutions as the Ministry of Foreign Affairs, the Japanese Imperial Army, and the South Manchurian Railway Company.

The Library of Congress digitized the Japanese Censorship collection in collaboration with the Japan's National Diet Library, recognizing the collection as a unique and incomparable historical resource.