Nagisa is Kojou's little sister who attends the same school as Yukina and is in the same class 3-C. She is also a close friend of Yuuma Tokoyogi and is good friends with Yukina Himeragi and Kanon Kanase. Her mother is Mimori Akatsuki. She is usually chatty with people she likes and is a very good cook.
Four years ago, she almost died in a train accident which was caused by demons, she was and still is traumatized whenever she sees a demon. She was actually traumatized after being possessed by "Root."
She first met Yuuma Tokoyogi after both Kojou Akatsuki and Yuuma retrieved her hat which was stuck on a branch at the end of a cliff. After they were safe everyone introduced themselves.
Abilities (after episode 16)
Psychometry: As a miko who carries the blood of a hyper adapater, she's been sought by universities and institutions to locate ancient ruins and decipher ancient epigraphs using her psychometry. However, she lost her powers due to trauma.
Avrora's Personality: Avrora's consciousness currently resides within her. Being the 12th Kaleid Blood, she is able to summon the 12th familiar Alrescha-Glacies. The abilities of this familiar are being able to decrease temperature below absolute zero.
Nagisa was a miko and had trained as a spirit medium with her grandmother. She also inherited the blood of a hyper adapter from her mother making her an extremely rare hybrid. After being attacked by the Black Death Emperor Faction she was left in a vegetative state and was brought to Itogami Island to receive special treatment. Unknown to others, Nagisa was being possessed by "Root." Roughly about three and half a year later, "Root" had awakened as the fourth primogenitor in Nagisa's body and hunted the other Kaleid Bloods to consume them. Having no memories of it's own, it began to feed on human's memories as memories are sources of magic and mass vampire turning incident occured creating havoc in Itogami Island. However, Avrora and Kojou managed to destroy "Root." Nagisa managed to transfer Avrora's consciousness inside herself just before she perishes. Since then, she lost her powers and any memories related to Avrora. After the incident, her mother became her personal physician.