In year 29 of the Divine Era, more than thirty years have passed since a mysterious monster from the heavens destroyed all of Japan except Shikoku. Young boys and girls, already unaware of the tragedy of that time, live in peace behind the wall that protect Shikoku. In such a time, there was a girl who was given the name "Yuuna" because of a special gesture she made at birth. Yuuna is an honorary name taken from Takashima Yuuna who perished in a fierce battle with the monsters about 30 years ago. Yuzuki Yuuna was one of those Yuunas, but contrary to her heroic name, she was a girl with no special powers. She learns that there is a girl in the same school with the same Yuuna name. Fuyou Lilienthal Yuuna — She says, "My dream is to go outside the wall and see the world for what it really is."