Tsugi no Giseisha wo Oshirase Shimasu: Kimi to Ko no Hateru Kotonai Kurayami wo

Morisaki Noboru, an ordinary high school student, suddenly reunites with Aoki Kana, whom he dated a year and a half ago. However, this reunion is not what either of them wanted, as they have been abducted by a malicious third party. Just as they are trying to sort out the incomprehensible situation, Asakawa Kaede and Sasagi Miki suddenly appear and tell them that they are currently on the 49th floor of an abandoned building, that it is an enclosed space with no way to get down to the floors below, and that there are other people in the main hall. They are then confronted with a shocking truth: they have been forced to take part in a "Serial Killer Game" where losing means death. Will Morisaki Noboru and Aoki Kana be able to escape safely?