These are kunai-like blades wielded by Izumo and Kotetsu. They have the general appearance of kunai with similar bases, but the blades instead are curved, elongated and single-edged, giving them similar appearance and function to swords. Each of the blades has a small hole right near its long, bandaged hilt, which at its edge sports a larger versions of the standard ring all kunai have. They are usually carried by Kotetsu, bandaged and strapped to his back. Izumo and Kotetsu can connect the two 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.