Actually its b rank. Youre just 2 ranks away from using it. I say keep the bio though.
Nuibari) Sewing Needle
Type: Weapon
Rank: B-Rank
Range: N/A
Chakra: N/A
Damage: N/A
Description:
Wielded by Kuriarare Kushimaru, the Nuibari is an unique weapon which assumes the form of a narrow longsword, cylindrical and very sharp which greatly resembles a large needle, with a long length of thin wire mirroring thread, tied to the eye located at the base of its hilt. This sword, quite aptly called "Longsword" is said to possess the ability to pierce all and stitch them together, clearly demonstrated by Kushimaru as how effortlessly he was able to penetrate multiple targets in a single thrust and then quite literally stitch them together in substantial bundles by simply pulling the attached wire taught. A capable user can even throw the sword with the intent of piercing a line of multiple enemies, before catching the needle at the other side and repeating the process at different angles, in order to create knots of corpses with the wire passing through the entirety, effectively creating bundles of bodies at various points along the length of the thread. The sword itself is virtually indestructible and is very resistant to damage though it can't pierce through physical techniques A-Rank and above. The metal wire is as resistant as the sword and although very sharp, the user will be able to pull and interact with it without injuring himself.
Note: Can only be used by Kuriarare Kushimaru