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 City, 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.
Souba is Japanese for "twin blade".
- Its appearance is aesthetically similar to the Arai Shakkū forged Satsujinken intended weapon Renbatō, wielded by the Juppongatana member Sawagejō Chō of the Meiji era set jidaigeki chanbara shounen anime and manga series Rurouni Kenshin.
- Contrary to popular belief, the Souba was not intended to be used akin to the Renbatō, where it would be used as a weapon to utterly render its opponent incurable of its wounds in its respective series.
- Like how Kadaj is a Remnant of Sephiroth, his weapon is significant of him being incomplete; the Souba can be viewed as a segmented and salvaged version of Sephiroth's signature Masamune katana in comparison.
- Kadaj carries a specially designed scabbard for the sword across his lower back; two parallel sheathes joined by a block between the mouths of the objects.