This kunai-like weapon is a blade. Kotetsu Hagane has two in his possession, which he uses in cooperate attacks with his partner Izumo Kamizuki. It's general appearance is that of a kunai, but the blade instead is curved, elongated and single-edged, giving it a similar appearance and function to a sword. The weapon has a small right hole right near its long, bandaged hilt, which at its edge sports a larger versions of the standard ring all kunai have. While not in use, Kotetsu keeps both his blades bandaged and strapped to his back. Izumo and Kotetsu can connect their blades with a chain attached to a weight, which they can use to wrap up an opponent.
After the final battle between Chiyo and Sasori, blades resembling kunai blades could be seen sticking up from the ground. This indicates that one or both of their puppet hordes used them. In the anime, Sasori's puppets are shown wielding sword-length kunai blades of various shapes.
In the manga, the kunai which the Prajñā Group used in their attack on Danzō Shimura were sword-like, lacked rings on the handles, and appeared to be about a metre long.