Swords are nothing new to Nari. All of his shinki save Akechi were different swords. This one? Just a little on the extreme side when the voice of Joscelin comes through. It's taking a lot of willpower not to just drop it and change his shinki back.

"No can do. I ain't killing anyone in here... We'll save that for an ayakashi fight, kiddo." Which, if Joss was like this just from being around other gods and shinki, it's going to be a hell of a struggle when it comes to ayakashi.