It is the end of the year in December.
Asumi has lost complete contact with her elder sister who goes to a graduate school in Tokyo.
Worried for her sister's safety, Asumi travels alone to Tokyo to find her–
but no trace of her could be found. Her sister wasn't in the laboratory where she had been assigned to, nor at her apartment.
Asumi is at loss as for what to do…
What has happened to her sister…?

Asumi is determined to find out.
What she doesn't know, however, is that she is in imminent danger…
and there are frightening facts awaiting her.
[From novelnews.net]