The “Inui Tower” of Osaka Castle is located in the northwest corner of the castle and was constructed in the early Edo period. This turret is not a building from the Toyotomi period, but was built when the Tokugawa Shogunate rebuilt the castle after the Osaka Summer Campaign. The Inui Yagura stood on top of a stone wall and played an important role as a defensive facility to prevent the invasion of outside enemies. The dry turret is one of the most important cultural properties existing in Osaka Castle, and the turret itself is a valuable remnant that demonstrates typical castle construction techniques. It is a three-story wooden structure with white plaster walls and black roof tiles, giving it an austere beauty on the outside. From a defensive standpoint, a narrow space was provided, which enabled effective defense against attackers. In the early Edo period, when Inui Yagura was built, the Tokugawa Shogunate sought to strengthen Osaka Castle as a base for western Japan and to demonstrate its authority. This turret was built as part of that effort, and was more than just a defensive structure; it also served as a symbol of Tokugawa power. After the Meiji period (1868-1912), Osaka Castle lost its function as a fortress, and some buildings and facilities were demolished, but the Inui Yagura miraculously survived. It escaped damage from air raids during World War II and has been preserved to this day. Therefore, the Inui Yagura is regarded as a valuable cultural asset that has accompanied the history of Osaka Castle.