An orphaned girl named Riko lives in the Belchero Orphanage in the town of Orth. The town surrounds a strange, giant hole descending deep into the earth, which is known as the Abyss. Returning from the Abyss can be dangerous as "the Curse of the Abyss," a mysterious and potentially fatal malady, manifests upon ascension. The deeper one goes, the more acute the effects of the curse; few who have descended into the lower regions have returned to tell of their experiences. Riko's longing in life is to follow in her mother's footsteps and become a White Whistle. One day, she discovers a half-human/half-robot boy in the first layer of the Abyss and names him Reg. A message from Lyza's White Whistle presumably for Riko, stating she is waiting at the bottom of the Abyss. Riko, determined to find her mother and secretly departs into the Abyss with Reg as her companion. source: Wikipedia