Tsukigase Kazuki, harboring a secret, enrolled at Saigishima High School on a remote island seeking anonymity. Saigishima was home to a place called "The Cove of Vanishing"—where, at summer's beginning, Kazuki discovered an unconscious girl. At the hospital, the girl awoke as Nanao, age 16, with no memories. But what did her whispered year—"1974"—mean?