In a world in which every corner has been explored, the Abyss remains the sole unexplored cavern. In this gigantic pit, the depth of which is unknown, weird and wonderful creatures live and valuable relics rest, the likes of which humans couldn’t dream of making. The wonders of the Abyss lure people to it, with many rushing to explore it. The adventurers who take up this challenge many times became known as Cave Explorers.
Riko is an orphan who lives in Oosu, a town built on the edge of the Abyss. She dreams of becoming a great Cave Explorer like her mother, and solving the mysteries of the Abyss. One day, Riko picks up a robot boy while exploring the cave.

Riko

Voice Actor: Miyu Tomita

Riko lives in an orphanage within Oosu and is lively and overflowing with curiosity. An apprentice cave explorer, her hobby is gathering the items that people have dropped into the Abyss. Her dream is to follow in the footsteps of her mother and become a famous cave explorer known as a 'white flute'.

「メイドインアビス」でリコの声を担当するのは、富田美憂さんです！ https://t.co/XdxKT3KH7W #miabyss pic.twitter.com/Rrfv4nTPil

— アニメ「メイドインアビス」公式 (@miabyss_anime) March 25, 2017

Regu

Voice Actor: Mariya Itou

Regu is a robot that looks exactly like a human that Riko discovered in the Abyss. Having lost its memories, Regu did not remember that it was a robot.

「メイドインアビス」でレグの声を担当するのは、伊瀬茉莉也さんです！ https://t.co/XdxKT3t5Jm #miabyss pic.twitter.com/oL6aSO0ZdC

— アニメ「メイドインアビス」公式 (@miabyss_anime) March 25, 2017

Nanachi

Voice Actor: Shiori Izawa

A strange creature that Riko and Regu meet on their explorations, with long ears and a fluffy coat.

ナナチのキャラクター紹介に、表情を追加しました。ナナチの出番は、もう少しお待ちください。 https://t.co/b2s3YJyLrp #miabyss pic.twitter.com/cBxfFOYrel

— アニメ「メイドインアビス」公式 (@miabyss_anime) August 11, 2017

Ozen

Voice Actor: Sayaka Ohara

A protector at the "Seeker Camp" who is an active as an explorer of 'white flute' called "Immovable Ozen". Her advantage point is incomparable strong muscle and height which is more than 2m.

オーゼンのキャラクター紹介を追加しました。 https://t.co/2F9MwkswGM #miabyss pic.twitter.com/07nmAOwhZu

— アニメ「メイドインアビス」公式 (@miabyss_anime) August 11, 2017

Maruruk

Voice Actor: Aki Toyosaki

She is a pupil of Ozen and explorer with "blue flute" even though she is still child. Her skin is not tolerable to sunshine, so she lives in "Seeker Camp".

マルルクのキャラクター紹介を追加しました。 https://t.co/8jr1cBYWzh #miabyss pic.twitter.com/vCzNO2I7EM

— アニメ「メイドインアビス」公式 (@miabyss_anime) August 11, 2017

Lyza

Voice Actor: Maaya Sakamoto

Riko's mother and legendary explorer called ”Lord Extarmination”. She hadn't been heard from since she set out "Last Dive".

ライザさん、初めてお顔が見えました！ #miabyss pic.twitter.com/ZJsaYemHF3

— アニメ「メイドインアビス」公式 (@miabyss_anime) August 25, 2017