Made from paper mulberry, kōzoshi is a strong yet light and supple type of handmade Japanese paper. The paper has many different uses—from applications in painting as a support and lining paper of Japanese-style paintings (nihonga) and paper for woodblock prints to everyday applications as paper used in Japanese screens, for copying sutras, for mounting pictures, and for lampshades. Paper with the special characteristics needed for the different applications is made in different parts of Japan through various manufacturing methods.

Paper mulberry, the raw material for kōzoshi, is a deciduous shrub in the mulberry family comparatively easy to cultivate. The paper uses bast fiber (fiber from around the stem) from the branches, which grow from the stump every year. Paper mulberry fiber is around 10-15 mm long. Because the fiber is thicker and longer compared to fiber from other plants used to make Japanese paper, such as gampi and mitsumata, and because it connects well with other fibers, finished paper made from paper mulberry is extremely strong and hard to rip. Areas in Japan that are famous for their high-quality paper mulberry include Nasu in Tochigi Prefecture and Tosa in Kōchi Prefecture. In recent years, however, paper mulberry is often imported from abroad.

Examples of kōzoshi include sekishu paper (Shimane Prefecture), hōsho paper (Fukui Prefecture), hosokawa paper (Saitama Prefecture), hodomura paper (Tochigi Prefecture) honmino paper and usumino paper (Gifu Prefecture), nishinouchi paper (Ibaraki Prefecture), and misu paper (Nara Prefecture).

The front side of the paper is the smooth side, and the rough side is the reverse side. Before using the paper for woodblock printing, make sure to place it between damp cardboard or newspaper until it is moderately damp. Various types of kōzoshi are available for purchase at painting stores and specialist Japanese paper shops.