Hakunagi

Hakunagi (Soul Cutter) is the Kusanagi given to Seireitou Hyuga during his training with orochimaru before the beginning of Naruto Omega. Like the original blade, it is indestructable and can cut through pretty much anything. Seireitou isnt shown using or holding this sword because he keeps it in Otogakure and later, in the Kitsune Realm because he uses KyuubiTaishou as his main weapon.

It cannot harm someone physicaly, shown that its blade goes right through a rock without touching it because this blade is a ghost-type, so instead, harms the soul, not the physical body. When infused with Chidori Nagashi, it can easily slice through and destroy the soul of a person.