Board Thread:Episode Discussions/@comment-1181222-20170823100207/@comment-734582-20170826075924

Hungry Ghost realm wrote: It aint forged, its a sacred weapon. Its like saying the sealing pot can be forged. Enma was dying to take it back with him, that means no one can recreate the original one. And btw sasuke's kusanagi cant extend and even then it phased through steel which means kusanagi can even become intangible. Someone at some point must've made the Kusanagi. Besides, the series itself calls Sasuke's weapon a Kusanagi, even though it's not an exact copy of Orochimaru's.

And like i said: Sasuke's weapon pierced Naruto's cloak when Shin's knives could not. It thus cannot be a "random weapon", even if we don't know the specifics. We do know that charging a weapon with an element can sharpen it beyond natural properties (e.g. cutting stone), and last time i checked, swords tend to hold their edges. A sword sharpened by chakra won't suddenly become dull once the chakra fades.