The “Fifth Water Gate” of Himeji Castle is part of the two-story “Ninotogatagura” that connects the main keep and the small keep, and serves as an important entrance to the keep's curving area. This gate is a double-opening, iron-plated corbelled gate with a side door. The upper turret has three iron-grille windows and a gun narrower on the outer side of the castle, and one wooden lattice window on the inner side, making it a solid structure to prevent enemy intrusion. In addition, on the south side of the floor, there is a spear drop against the five gates of water directly below, reinforcing the defensive function. In this way, the five gates of water and the second watchtower played an important role in the defense of Himeji Castle.