Series by 三部けい

Minato Myojin and his younger sister, Nagisa, are two young siblings who have spent their days waiting for their long-absent mother to return home. One day after school, their mother reappears, proposing a sudden trip to an amusement park. Minato feels a mix of relief and unease at her unexpected return and her odd behavior. Leaving their mother behind, the siblings board a Ferris wheel, but a sudden lightning strike throws Minato into confusion. When he comes to, Nagisa is gone, replaced by the lifeless body of an unknown woman, and the reflection in the window shows a stranger's face staring back at him.