A cheerful and curious girl from an orphanage in Orth, a city at the edge of the Abyss. Her dream is to become the legendary Cave Raider [White Whistle], just like her mother, Lyza. She decided to dive deeper into the Abyss after finding Lyza's White Whistle.

Found in the abyss, a robot that looks identical to a human. Having lost his memories, he does not remember his name, let alone the fact that the he himself is a robot. He is exploring the Abyss with Riko.

Originally a human, after taking part in Bondrewd's curse experiment, now takes after a fluffy and furry form. After meeting Riko and Reg on the fourth layer, Nanachi joins them in their adventure.

A White Whistle Cave Raider living in the fifth layer of the Abyss. Also known as the "Sovereign of Dawn". He is Prushka's father. He used to conduct experiments with children as test subjects, which turned Nanachi into her current form, and made her part of his experiments.

The daughter of Bondrewd. She has never been to the surface in her entire life. Bondrewd gave Meinya to her when she became 10 years old.