A is a special-made metal that can be infused through "chakra flow" with elemental chakra or even Yin–Yang chakra to produce added effects. According to Shikamaru, the blades are able to absorb the chakra type of the user, and become the origin of a technique, for the user. After Asuma's death, the blades come into Shikamaru Nara's possession, which he used by infusing his chakra and striking their shadow with it to completely immobilise them. Years later, Shikamaru passed these blades own to Asuma's daughter, Mirai Sarutobi.