Otherworld Barbara

(from ebookjapan):

The year is 2052. Tokio Watarai, a "dream guide" who can enter other people's dreams, takes on the job of searching the dreams of Aoba Jujo, a girl who has been asleep for seven years since a certain incident.

And with the name of the island where Aoba lives happily in her dream, "Barbara", unexpected facts begin to appear one after another...?

Official English

• Won the Japan SF Taisho Grand Prize in 2006