This girl's navy pleated skirt is part of a school uniform. The skirt has a back zipper (pulling from the seam), and is missing either a button or a clasp at the waist. The fabric is a cotton/polyester blend.
This skirt is part of a "sailor fuku," a common style of uniform worn by female middle school students. The uniform generally consists of a blouse attached with a sailor-style collar and a pleated skirt.
The Japanese school uniform, also known as seifuku, is modeled on European-style naval uniforms and was first used in Japan in the late 19th century. During the Meiji period (1868-1912), the country was flooded with many styles of Western dress, especially long dresses and trousers. Styles were sometimes mixed; students would wear either Western style uniforms or clothes showing both Western and Japanese influence. Today, school uniforms are common in many of the Japanese public and private school systems.