Also known as the Daireishokairō is a repository of all the knowledge and history of the Soul Society. This is another area to which access is restricted. As a result, few are familiar with its inner workings even among the captains. Ukitake was placed in charge of investigating the library's circuits to identify anything that Aizen may have researched during the time in which he was believed to be dead. Ukitake's investigation discovered that Aizen had accessed much data on the Hōgyokuand the King's Key.