The menacing man introduces himself as Daichi Nagaoka, an old associate and former Hand Shaker partner of Makihara. He also introduces the white-haired girl beside him as Mayumi Akutagawa, who is none other than Koyori's twin sister. Koyori's sinister past is revealed through a flashback concerning both Makihara and Nagaoka, as well as the Akutagawa professors...