The Iryuuhin (失われた文書; lit. Lost Article) Archives was once an extensive system of Shinigami arts and history. Essentially a library sublevel, the Iryuuhin Archives section was arguably the oldest section of the Shinigami Academy. One day many centuries ago, it was believed to have collapsed underground. Although a library system was rebuilt, much of the information stored in the archives were lost, including many of Soul Society's oldest spiritual arts. While practicing teleportation Kidō, academy student Takashi Ishigawa unintentionally apported himself deep underground, into the lost archive. He then discovered where he was, and that the archives were not completely destroyed, but had simply fallen deeper underground. Viewing the Iryuuhin Archives as his own personal treasure, Ishigawa never told anyone of his discovery.