The story starts with a girl dreaming of falling, and falling, and keeps on falling without stopping. Suddenly, she awakens, and finds herself in a strange room - or something with a soft wall.
A girl/Haibane named Reki finds a huge cocoon growing in a room inside of the "old home" and that's where the dreaming-girl finds herself upon awakening. The girl is deeply confused. She doe not know where she is or how she got there, or where she came from or even who she was.

Then she hears voices coming from outside.

Reki and the other girls in the "old home" have found the cocoon. Apparently, they know exactly what is happening, and what to expect, and they are very excited and gleeful. It's because a Haibane is born from a cocoon, which means another one of their kind coming to an existence to start sharing the "old home" with them. When the girl finally makes her way out of the cocoon, she receives a very warm welcome from the girls with grey wings and halo. They name her Rakka (meaning "falling") because a Haibane is named after the dream she awakens from.

Not unlike "Serial Experiments Lain," everyday lives of extraordinary people are told in a realistic yet slightly askew manner, which is creator Abe's specialty. The main theme was written by Kou Ootani, well known for the scores to Gamera, Gundam Wing, and You're Under Arrest(Taiho Shichauzo) and also as the producer for enormoualy popular band, Dreams Come True. The ending title theme is by Heart of Air who have been credited for music to Azumanga Daiou, Z.O.E., and Sister Princess(game).