Kobunin was a facility considered to be built by WAKE no Hiroyo in Heiankyo (the ancient capital of Japan in current Kyoto) at the beginning of the Heian period. It was commonly accepted that Kobunin played the role of daigaku besso (adjunct facility of daigaku-ryo - Bureau of Education under the ritsuryo system) of the Wake clan (mentioned later), but became defunct before long.
The entry for the date when Hiroyo's father WAKE no Kiyomaro died (April 4, 799) in "Nihon Koki" (Later Chronicle of Japan) contains the description that -- Hiroyo concurrently assumed the offices of Shikibu shoyu (Junior Assistant of the Ministry of Ceremonies) and Daigaku Betto (Chancellor of the University) (Daigaku no kami; Director of the Bureau of Education), and, as his father Kiyomaro had wished, located his private residence south of the daigaku-ryo the Kobunin where he collected thousands of Chinese classics from inside and outside Japan, and donated 0.4 square kilometers of new rice fields for awarding scholarship funds. It was impossible to know when the Kobunin was founded mainly because "Nihon Koki" was scattered and ultimately lost; but from the other records of Hiroyo, it was estimated that the Kobunin was founded from the end of the Enryaku era (782 - 806) to the beginning of the Daido era (the first year of Daido was 806). Although the role of the Kobunin described in "Nihon Koki" was the same as that of the other daigaku besso; since the Kobunin was founded a little earlier than the other daigaku besso including Monjoin and since few record on the Kobunin was left, it was unknown whether it had the same purpose as that of the other later daigaku besso from the beginning or not.
In response to the question, Hiroyuki MOMO (Japanese historian) inferred that the Kobunin had established as daigaku besso of the Wake clan at the latest when Kangakuin (daigaku besso of the Fujiwara clan) and Gakkanin (one of the daigaku besso) were founded around the Konin era (810 - 824) and the Jowa era (834 - 848). On the other hand, Yukio KUKI (Japanese educator) paid attention to the description 'Chinese classics from inside and outside,' interpreting 'inside and outside' as Buddhist books and the other books, and pointed out that if the Kobunin held Buddhist books, it was inconsistent with the fact that the daigaku besso was an institute for students of Japanese daigaku-ryo which had ostensibly excluded Buddhism -- Then, he inferred that the Kobunin was not the daigaku besso but a library.
Partly because the Wake clan was not so prosperous after Hiroyo died, it was considered that the Kobunin was shortly ruined. Since the entry for August 31, 848 in "Shoku Nihon Koki" (Later Chronicle of Japan Continued) contains the description that lightning struck in Heiankyo and damaged some buildings, which included the Kobunin, and since a Chinese poem ('秋夜宿弘文院') supposedly composed by SUGAWARA no Michizane when he visited the Kobunin in 885 was contained in "Kanke bunso" (an anthology of Chinese-style poetry by SUGAWARA no Michizane) in 885, it was estimated that the Kobunin had existed at least for 80 years after it was founded. From the description in "Saikyuki" (record of court practices and usage written in Chinese style) written by MINAMOTO no Takaaki supposedly written in the mid tenth century that the Kobunin had been already ruined, it was estimated that the Kobunin was defunct shortly after the days of Michizane.