The Lion Agency and the Taishi Bureau have conducted a joint investigation on an unidentified marine accident occurring in the sea area around Itogami Island. On the other hand, Kojou wakes up after hearing a voice. The spectacle that jumped into his sight, whose memory was also dim, was a blanket and a cheek that seemed to have been wrapped and sleeping, cheeking, and Yukina's face appealing with tears. "Senpai ... I lost something important ...".