A Shadow Weapon, also known as a Dark Arm in the Funimation dub, is a weapon who can transform into Japanese weaponry befitting that of a ninja/assassin. Black☆Star is the only known Shadow Weapon meister within the sereis. Both Tsubaki Nakatsukasa and her brother, Masamune Nakatsukasa are known Shadow Weapons. It's possible that the Nakatsukasa Clan are also Shadow Weapons.