Itachi's Sword of Totsuka remains a curious mystery, since the other Susano'o abilities are an extension of the user's power. But the Totsuka sword is an external item that Itachi obtained and somehow fused with his Susanoo rather than being an intrinsic component of the Susano'o itself. It isn't a Susano'o ability like Sasuke's Amaterasu arrows or Obito's Shuriken or Itachi's own Yasaka beads, but rather an add-on item that Itachi must have discovered and then acquired for himself. It's the only known weapon that could be fused with the Susanoo, although precisely what properties the sword had is unknown.
Apparently, the Sword of Totsuka was a famous blade that Orochimaru was searching for, as the sannin wanted the sword for himself.
Ups! Tento obrázek porušuje naše pokyny k obsahu. Před publikováním ho, prosím, buď odstraň, nebo nahraď jiným.
Ups! Tento obrázek porušuje naše pokyny k obsahu. Před publikováním ho, prosím, buď odstraň, nebo nahraď jiným.
Since Orochimaru knew of the sword's existence, and itachi did too, apparently, whether he actively searched for the powerful blade or whether he just happened to stumble upon its former owner and took it for himself is unclear. But the blade apparently had some sort of legend or rumors surrounding it. One has to wonder what kind of stories surround such a mystical blade.
Zetsu describes it as a spirit blade without physical form. Since it's melded to Itachi's Susano'o, it vanishes with Susano'o when Itachi extinguishes his red chakra avatar and it reappears when he activates Susano'o again.
Since it's a sword made of spirit, it has unusual properties and I have no idea how the sword works, where it could be found, how Itachi found it, and what properties it had that made it able to fuse with a Susano'o. It is intriguing to imagine how one would locate a sword that doesn't have a physical form, but how Itachi discovered it is an adventure that remains a mystery.
The blade seems to operate similarly to the Death Reaper Seal, as it has the brutal effect of sealing someone away in a genjutsu stupor for all time, according to Orochimaru.
Admittedly the implications it has for Nagato's fate seem very unpleasant, since apparently Nagato might be destined to suffer in a gnejutsu for all eternity now that Itachi sealed him away with the Totsuka sword, forever separated from his friends in the afterlife, which is a pretty savage fate.
