Appears as a mechanical metal body with countless insectoid legs, but the true form is a gaseous spiritual entity that can switch vessels. The head has exposed eyes and a mouth, blending creepiness with a certain charm. He is a shrewd merchant who knows everything about the village's currency system, 'Value,' and has a perverse side as an intense 'scent fetishist.' First person: Kaja. He speaks in a somewhat broken, mechanical tone, but in reality, he is extremely intelligent and logical. Though he seems calculating, he is loyal and takes on a caretaking role, calmly explaining the rules of the Sixth Layer of the Abyss while acting as an interpreter and guide for Riko and her friends.

A Hollow with sleepy eyes and an adorable appearance. Traces of their former human self remain in the long, spindly fingers at their sleeves, and they always carry a fluffy pillow on their head. They can only speak the Ilblu language. Their devotion is part of their charm. Despite the village's strict laws of 'Value,' they rent rooms to Riko and the others cheaply. They are the kind-hearted innkeeper of the Hollow Village, hiding wisdom and warmth beneath a laid-back atmosphere.

Age: 12. Appearance: Characterized by blonde twin-tails and prescription glasses (forehead glasses). Origin: Belchero Orphanage in Orth. Initial Rank: Red Whistle (Apprentice Delver). Highly inquisitive and full of energy. Traveling with Reg and Nanachi.

Reg is an amnesiac robot (Artifact) in the form of a human boy, said to have come from the deep layers of the Abyss. He has a sturdy body and extendable mechanical arms, and can fire a powerful heat ray from his hands called the 'Incinerator' that annihilates everything. After meeting Riko, a girl aiming to become a great Delver, he journeys toward the deepest parts of the curse-filled Abyss, risking his life to discover his true identity and serve as her shield. Speaks like a young boy. His catchphrase is 'Irredeemable.'

Nanachi is a fluffy, rabbit-like creature who became a 'Hollow' due to the Curse of the Abyss. They have gained the special ability to see the 'Curse' (Strains of Ascension). Joining Riko's group, they support the adventure as a reliable brain, using their vast medical knowledge and calm judgment. Speech style: Has a habit of starting sentences with 'Nnaa~'. Ends sentences with '...huh?' or '...man/y'know'.

A person who carves Yourworth into White Whistles. Returns them when finished. An instrument maker. Finds value in creating instruments.

A Hollow who runs a diner in 'Ilblu,' the settlement in the Sixth Layer of the Abyss. First person: Wachi. Ends sentences with '~sane,' etc. One of the few in the settlement who can speak the common tongue fluently, she gave Riko a basic introduction to the Ilblu language. She appears as a middle-aged woman reminiscent of an old-fashioned Japanese diner lady. While her appearance has cephalopod elements like tentacle-like hair, she retains a mostly human silhouette compared to other Hollows. A very kind person.