Tsuki wa Higashi ni Hi wa Nishi ni: Operation Sanctuary  

Hani Hani: Operation Sanctuary, The Moon is East, The Sun is West: Operation Sanctuary

Naoki Kuzumi was a high school junior who lost his parents in an accident five years ago and lived with his aunt, uncle, and cousin Matsuri. Despite this, he considered his life ordinary except for the fact that he couldn't remember anything from his childhood. On a sunny day while taking a nap on a bench, Mikoto, a redhead girl, fell onto him from the sky, thinking he was her younger brother Yuusuke. She had traveled back in time to Naokis era because she heard that he was living in a time period where many people were suffering from an incurable disease.