Anime: Hani Hani: Operation Sanctuary
Naoki Kuzumi, a junior in high school, had lost his parents in an accident five years ago, and is living with his aunt, uncle, and cousin Matsuri. He always thought his life was ordinary, besides the fact that he cant remember what happened in his youth. One sunny day as he is taking a nap on a bench, a redheaded girl Mikoto literally falls on him from the sky. For some reason, she thinks hes her younger brother.
Naokis time period is a temporal shelter for those in the future, when many are suffering from an incurable disease. When she heard her younger brother Yuusuke had been taken to Naokis time, Mikoto herself had gone back in time.