Kurumi Tokisaki is the main antagonist in the series. She is the third Spirit to be encountered in the series and is the most dangerous and lethal Spirit. She is heavily obsessed with Shidou and has the ability to manipulate time. Her codename is Nightmare. She has a split personality: that of a gentle, mysterious high school girl with a slow talking pattern, and that of a psychopathic killer. Kurumi is very aggressive in her actions which makes it harder for Shidou to capture her.
Mana reported that Kurumi is the most dangerous spirit known, who has personally killed over 10,000 people which does not include the spacequake’s victims within that statistics. Kurumi used unstated and unexplained methods to personally transfer into Shidou Itsuka’s high school and classroom so she can get closer to him. Her purposes and reasons in this transfer are simple; consume Shidou Itsuka, in doing so gain their memories, goals, fears and obsessions. In some non-canon stories, the clone Shido seduced shows some “independent” attitude, almost rebellious, and openly acts lovey-dovey with Shido, which causes troubles to the “main” Kurumi and even leads to confrontation with her.
These clones are less powerful than Kurumi herself as she has mentioned in the last chapter of volume 3 and in the epilogue of volume 4. She can form a single clone by shooting herself with Zafkiel or bring out all of her clones at once from a pool of shadows which she also uses to draw them all back in and all the time they’ve collected. She can also call her clones partially through small fields of shadows, most often to hold someone in place and prevent them from moving.
To activate any power she needs, she first needs to call her Angel (regardless of whether or not the Angel has been summoned already or not), and to position both of her guns just like a clock: The musket on 12 and the flintlock points at the number of the bullet. Next she needs to shoot the bullet at the target with the hand gun. In case she needs it for herself, she will be required to shoot it at her head.
She also has the ability to call and dismiss spacequakes at will, as shown in the series while she confronts Shidou on the school’s rooftop.
It’s also hinted that the experiences a clone lives affect the the main one since, after helping Shidou locate Tohka (so Kurumi could track the Second Spirit) and parting ways, Kurumi is shown talking to her clones and being happy because she received a pat on the head from Shidou.