The Hakurouken(楼観剣) and Roukaken(白楼剣), are weapons used by Youmu Konpaku. Hakurouken or the Lookout-Tower Sword is long blade katana is said to be made by youkai and can not be wield by normal humans; It's said that it has the power to kill ten spirits in one stroke, but as one cannot actually kill spirits, it's unknown how true this could be. The Roukaken or the White Tower Sword is the is the ancestral sword of the Konpaku family. It had the power to dispel the confusion of those it cuts. That is, using it on ghosts will cause them to attain enlightenment (Sikieiki said that what she's doing on the spirits was a form of "cheating"), and using it on humans will cause them discomfort and a bit of pain.
In Perfect Cherry Blossom,Imperishable Night,Phantasmagoria of Flower View and Shoot the Bullet, Youmu wield both of the swords. Except on Immaterial and Missing Power and Scarlet Weather Rhapsody. Many fans doubt why she never used both of the weapons at once.