"Eisei Bunko" is the name of a foundation established to retain and care for ancestral works of art, literary manuscripts, and other historical materials (ancient texts, records, illustrations, etc.) of the Hosokawa family, who were once the daimyo of Kumamoto. In 1964, several pieces from the collection kept in the storerooms of the Hosokawa Kitaoka Mansion in Kumamoto City were entrusted to the library of Kumamoto University. These continue to be used in educational research conducted by the Faculty of Letters of the University.
The Eisei Bunko collection represents the archives of one of the greatest daimyo families, including several historical articles concerning almost every aspect of human activity during the Edo Period, from politics, economics, administration, legislation, and social activism, to medical and pharmaceutical science, architecture, philosophy, and art culture, as well as rare manuscripts of literary works of art that were kept in hand by the successive generations of feudal lords.