The Souba is a katana with two reinforced parallel blades, set a small distance apart from each other. The design's intent is to trap an opponent's blade between them and disarm them. Kadaj wields and holds Souba as a normal sword when confronting Cloud in the Forgotten Capital, but fights holding it in a reverse grip when fighting Cloud in Midgar at the end of the film. Despite it being much smaller than the Fusion Swords, Kadaj is able to battle Cloud with the Souba with no apparent handicap, taking advantage of the dual blades' wider striking range to more easily deflect Cloud's attacks.
The blade is lost in the ruins of Midgar during his final battle with Cloud, but after Kadaj reforms into Sephiroth and is subsequently defeated, it regenerates with him. Following his death in Aerith's Great Gospel, both Kadaj and the sword vanish into the Lifestream.