Nyoi Rentou (如意練刀, Nyoi Rentō, Refined Blade At Will) is the Metal Vessel of Kouha Ren. It gets its power from Kouha's Djinn, Leraje. It has the ability to change its size at Kouha's will. Nyoi Rentou has an incredible cutting power. One slash down can make huge splits in the ground. Because of how heavy Nyoi Rentou can get, Kouha has to make it huge right when he attacks.