Doko yori mo Tooi Basho ni Iru Kimi e

The story centers on a boy named Kazuki Tsukigase, who transfers to a high school on a remote island to get away from anyone who knows him. Kazuki finds out that there is an inlet on the island where people are rumored to disappear. Exploring the inlet, he encounters an unconscious girl. When she comes to after Kazuki takes her to the clinic, she is unable to give out anything about her identity except that she is named Nao, is 16 years old, and whispers the year "1974."
(Source: Anime News Network, edited)