Code Name: Nightmare Kurumi is the third spirit who appeared after Tohka and Yoshino. She has a split personality: that of a gentle, mysterous highschool girl with a slow talking pattern, and that of a psychopathic killer. She is very aggressive in her actions which makes it harder for Shidou to capture her.
Kurumi has the archangel Zafkiel, and has the power to control over time. The reason why she keeps appearing after being killed by Mana countless times was because of her powers. For example, she can heal herself by turning back the time. She uses a gunblade as her weapon. Though she always keeps getting killed by Mana, Kurumi from a different time period appeared and was considered as the most deadly of all took down Mana, Tohka, and Origami at near end of volume 3. It is said that her ultimate goal is to get the powers of the spirit inside Shidou to kill the very first spirit who appeared 30 years ago to make all spirits disappear from this world. Her angel is destroyed by Kotori in volume 4.
The twelve Roman numerals on the clock in her left eye have different powers that only the original Kurumi can use, but by using their powers, it will cause her life to be eaten away. In order to avoid this, she kills people to obtain 'time'.