Taking place one month after the events of the film Heaven Is a Place on Earth. Nagi returns to her former ways of living at the Sanzenin Mansion, until she receives news from American officials alerting her that she has a week to pick up her late father's things, which had been permanently delayed owing to different situations. Nagi encounters a mystery girl (with a secret goal) claiming to be Nagi's little sister after getting news of her father, whom she does not remember. The series offers a fresh plot that is unique to the anime and is not based on the manga in any way. Kenjiro Hata, the main creator of the original series, devised the initial concept for the plot of this anime.