This turret was designed and constructed by Enshu Kobori in 1620. This Turret, as well as Inui Turret at the northwest corner of Nishi-no-maru Garden, is one of the oldest existing structures of the Castle. The name of the turret is said to have been derived during the Ishiyama War, when Nobunaga Oda's forces had a difficult time penetrating the Castle due to the onslaught of arrows from this corner turret. Nobunaga and his men were reportedly willing to pay the high sum of sen (1000 in Japanese) kanmon to break through the strong defense, and thus the name Sengan Turret. When the Turret was disassembled for restoration, a piece of board bearing the note written in Indian ink "Putting -up the ridge beam on September 13, 1620", was found, and thus the date of the ceremony for laying roof of this was confirmed.