>>4371049obviously spoilers
Nanachi is the result of horrific human experiments on orphaned children, who carried around her best friend after they were turned into a sentient doormat. her first arc revolves around gaining the courage to end her friends miserable existence, and her character after that has a lot of "dealing with the guilt of killing my best friend after she was made into a sentient doormat"
she canonically smells irresitable to Reg and others and is frequently "fluffed" by Reg. She is also possibly immortal (not invulnerable though as the last chapter showed, RIP) but this is speculation on my part
Faputa is similar but instead of human experiments it's more like a monkeys paw. a rape victim was forced to wish on a magic stone for her villiage to live forever. this caused her to be was turned into an eternal food source (by having babys that immediately die and can be used as food, and also she was turned into a magic flesh-villiage (exactly how it sounds) that they live in) for the villiagers who were now immortal for the same reasons Nanachi might be, except they aren't all cute they all look fucked up. She then wished for a baby that didn't become food, and gave birth to the immortal Faputa, who, as a result of her mother's third wish kill (either revenge or mercy) all the now eternally suffering villiagers, wants to commit murder unending. She loves Reg because she met him in Reg's past life as The Terminator before he became Astro Boy.
Faputa is canonically a liquid according to in-universe field guides by Riko.
She puts "sosu" at the end of every sentence because that's what royalty is supposed to do.
Made in Abyss is really fucked up when you recap it like this. i might be missing stuff, it's been years. we only get 1-3 chapters a year on a good year