Nanachi is so-called "Final Form"—a survivor of ascension from the sixth level of the Abyss. Madness and/or death are not uncommon results of such an attempt but, due to certain circumstances, Nanachi was able to keep their personality and mental faculties intact; their body, however, was deformed beyond recognition.

Nanachi's gender or sex are never expressly stated. Talking about themselves, Nanachi uses the gender-neutral pronoun "oira."

Not much is known about Nanachi's past—they were born in the Far North region of Sereni, lost their family and home at a young age and were taken to the Abyss by treachery.

Nanachi looks very young, but their vast knowledge of the physics and ecology of the Abyss seems to suggest they've lived there for quite a while. They also appear to be an accomplished healer with significant surgical skills and extensive knowledge of medicinal plants and such. Most of the time Nanachi is cool and reserved, keeping their distance both emotionally and physically. Their ironic attitude often borders on being sarcastic and even cynical; however, behind this mask, Nanachi hides a kind and gentle soul capable of deep compassion and selfless devotion.

(Source: Wikipedia, edited)