A psychological thriller centered on Sakai Yoichi, a freelance video director, and Mitsumi Kei, a piano teacher who moonlights as a serial killer. When Yoichi, who is stuck in his current situation doing small jobs to make ends meet, returns to his office, there's a package waiting for him. Inside is a human finger, and the message for Yoichi to get in touch if he's interested to "document his activities." Yoichi was going to call the police, but after considering, he decides instead to contact the sender. The person he meets at the designated house is none other than pianist Mitsumi Kei. This encounter leads Yoichi to continue documenting the murders, but what awaits him as a result of this decision... remains to be seen.