Roukanken and Hakurouken

The Roukanken (楼観剣, lit. "watchtower sword") and the Hakurouken (白楼剣, lit. "white tower sword") are weapons used by Youmu Konpaku.

Roukanken

Roukanken is a long-bladed katana said to be made by youkai and cannot be wielded 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, the truth of this claim is debatable. Youmu herself claims that "The things that cannot be cut by my Roukanken, forged by youkai, are close to none!". Perfect Memento in Strict Sense echoes this claim, though it's likely that Hieda no Akyuu is simply quoting Youmu.

Hakurouken

Hakurouken is the ancestral sword of the Konpaku family, which only they are capable of using. It has the power to dispel the confusion of those it cuts. That is, using it on humans will cause them minor pain and discomfort, while using it on ghosts will send them to nirvana (Eiki Shiki, Yamaxanadu has said that what Youmu is doing to the spirits is a form of "cheating").