A demon weapon partnered with Black Star hailing from the Nakatsukasa Clan, a special weapons clan who are direct descendants of demon weapons created by the mother of magic weapons, Arachne Gorgon. Having inherited the unique Multi-Form Ability of her clan, she joined the DWMA to stop her brother from becoming a kishin, becoming fast friends with Black Star in the process. Tsubaki is known to be very patient and forgiving, with a polite and gentle personality that often leads to her helping or comforting her friends when they are in need.