Chigusa Amagasaki is a practitioner of onmyōdō, the traditional Japanese art of charms and spell-casting, and operates as a rogue agent affiliated with the Kansai Magic Association. She serves as a primary antagonist during the school excursion arc, actively working to undermine the fragile peace between the eastern and western magical communities of Japan. Chigusa harbors a deep-seated grudge against Western mages, driven by the trauma of losing her parents to Western wizards during a great magical war that occurred twenty years prior to the events of the story. This personal tragedy fuels her overarching motivation: to enact revenge on Western magical society by summoning the powerful demon god known as Ryōmen Sukuna-no-Kami. To accomplish this summoning, she requires an immense source of magical power, leading her to target Konoka Konoe, a young girl who possesses vast, untapped magical reserves. Chigusa's personality is characterized by her intense hatred and her determination to disrupt any diplomatic progress between the magic associations; she actively tries to prevent the young mage Negi Springfield from delivering a letter to the head of the Kansai Magic Association, as she fears improved relations would thwart her plans for revenge. In her efforts to kidnap Konoka and execute her scheme, Chigusa employs a variety of abilities, including the summoning of warrior spirits and the creation of shikigami, which are paper familiars that can take various forms. Notably, her shikigami are often small, animal-like creatures, such as frogs and monkeys, but she is also capable of summoning larger, more formidable entities like ogres. She further supports her operations by enlisting three mercenaries and using disguises, such as posing as a train station vendor or hotel employee. Despite successfully using Konoka's magic to awaken Ryōmen Sukuna-no-Kami, the demon god is swiftly and easily defeated by the powerful vampire mage Evangeline A.K. McDowell. Following the failure of her plan, Chigusa attempts to flee but is captured by Chachazero, Evangeline's doll partner. She is subsequently taken into custody by the Kansai Magic Association, effectively ending her plot for revenge. Her name is noted to have been taken from a member of the manga author's own staff.