Nanachi (ナナチ, Nanachi) is a Narehate; a person who survived the 6th layer's curse of the Abyss, and was left deformed as a result, but, unlike most other narehate, still retained a sound mind. Possessing vast knowledge of the Abyss - its ecosystem, vegetation and even the use of the medicines, Nanachi is currently a part of Riko's party, assisting her in reaching the bottom of the Abyss.
Nanachi's appearance is very rabbit-like, save for a long sturdy tail and human-like hair; which is straight and white or cream in a short bobbed style, the sides of the bangs going down to the shoulders. In contrast, medium tan fur covers the rest of Nanachi, with light tan covering the insides of their ears and belly. They have a blush-like spot on each cheek; which has two thick whiskers protruding sideways. Other animal traits include a cat-like mouth with little fangs, yellow eyes with horizontal oval shaped pupils (similar to a goat's) and erect bunny ears. Their fingers are rather stubby.
Nanachi's attire consists solely of grey-green, baggy, drop-crotch harem pants, with dark-pink hip-bags on both sides, red pant legs, and a pink flap that is supposed to cover their usually naked torso.
Nanachi also wears a large, oddly-shaped headpiece the same colors as their pants. Attached to the sides of it are two curved horns that stick out horizontally. Hanging from the back there is a large layer of what appears to be shingles, covered by a layer of cream-colored animal pelts, and then another smaller layer of shingles. Strangely, Nanachi's side bangs seem to be much longer when the helmet is on, going down to their hips. They are tied at the end with metal rings. It is likely that these hair extensions are a part of the headpiece.
They typically walk upright, but sometimes will run on all fours if they are trying to move quickly.
Most of the time Nanachi is cool and reserved, keeping their distance emotionally and physically. Their 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. They are also quite bashful when complimented, seen in their reaction to being called "fluffy". They also express discomfort at being petted, especially by Reg.
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 was taken to the Abyss by the infamous white whistle Bondrewd, along with many other children.
Bondrewd was experimenting with ways to negate the curse of the abyss, using children as his test subjects. While in the Abyss, Nanachi meets Mitty, another child taken by Bondrewd, and the two became close friends. Eventually, the number of children decreased, until finally Mitty was chosen to be experimented on and was led out by Bondrewd. Worried for Mitty, Nanachi followed, and soon found her trapped in one of two connected capsules. Walking in at that moment, Bondrewd then decided to use the two as test subjects together because of their strong relationship, as previous experiments with humans and animals had not been effective. Nanachi was then forced into the other capsule, lowered to the 6th layer, and then quickly brought back up. The capsules were designed to transfer the curse onto only one subject, Mitty, leaving the other potentially unaffected. Both survived and became Narehate as a result, but Nanachi retained their humanity and mind, as the majority of the curse was transferred to Mitty.
Nanachi, in their new Narehate form, continued to work for Bondrewd at Idofront, helping him to create Cartridges. Unable to bear the horrible experimentation Mitty was subjected to any longer, Nanachi escaped Idofront with Mitty on their back. The two traveled up to the 4th layer, where Nanachi found a spot away from the Abyss' vertical shaft where the force field was not present, and constructed a hideout there. Nanachi lived peacefully with Mitty in the fourth layer for some time. Sometimes delvers would pass through the area, and fearing that word of them may get out, Nanachi was careful to not reveal themself, and instead would watch from a safe distance. Occasionally, when a delver was wounded beyond help, Nanachi would take them in and experiment on them, hoping to find a way to kill Mitty. The bodies of these delvers are buried in a graveyard behind their hut.
Nanachi does reveal themself to Riko and Reg after seeing Reg crying over Riko's body. Because the two's relationship reminded Nanachi of their relationship with Mitty, Nanachi decided to aid them. During their stay Reg demonstrated the power of his Incinerator, which reminded Nanachi of Bondrewd's relic Sparagmos; the only thing that had been able to permanently injure Mitty. Seeing the opportunity, Nanachi asked Reg to kill her, releasing Mitty from more suffering, to which he reluctantly agreed. After Mitty's soul was released, Nanachi decided to join Riko and Reg on their journey to the bottom of the Abyss.
Mitty was the only one of the other children to approach Nanachi, the others complaining that they smelled bad. Mitty was impressed with Nanachi's artistic skills and knowledge, and asked to pair up. Nanachi was reluctant at first, but Mitty insisted, and her gentle enthusiasm quickly won Nanachi over. The two grew very close, and were practically inseparable. One possible interpretation is that Nanachi may have even had romantic feelings towards Mitty, as Nanachi would blush at Mitty's compliments or when they were in close quarters, and would draw pictures of her absentmindedly. The two often held hands, hugged, slept side by side, and were generally very intimate with one another.
During Bondrewd's experiment, just before the two ascended from the 6th Layer, Mitty's last words were a tearful proclamation that she wished for her soul to accompany Nanachi if she did not survive. Mitty did survive, but was left in a permanently unrecognizable state — transformed forever into a Narehate, and cursed with immortality. After seeing Bondrewd's relentless torture of Mitty's new Narehate form, Nanachi escaped Idofront with Mitty and vowed to free Mitty's soul from her current physical state. Until that day, their hideout in the 4th Layer was filled with all sorts of books, homemade plushies, and pillows and blankets, all with the goal of enriching Mitty's life. Nanachi treated her as if she was still a self-aware being, and would talk and read books to her. Despite their peaceful living, Nanachi felt that Mitty was their only reason to be alive, and had planned to take their own life after her death was accomplished. Nanachi felt very strongly about this mindset, going so far as to call Reg cruel when he made them promise not to.
When the day came, Nanachi set up a large nest full of pillows and other items they had made for Mitty, so that she could be in comfort even as she was being released. Nanachi said their goodbyes, telling Mitty they would meet again. Only a minute later they recanted this, saying instead they would always be together. When the deed was done, Nanachi fell to their knees and cried intensely, proclaiming Mitty to be their "treasure".
Nanachi copes with their loss by telling themselves that they will one day meet Mitty again, though they stated that they don't really believe this will happen. Even so, Nanachi holds onto hope with belief that everything returns to the Abyss, and has even been preparing for their fated meeting by learning how to cook good food.
Nanachi first encounters Reg when the robot was attempting to save the life of Riko - who had undergone the strain of the fourth layer and also was poisoned with Orb Piercer venom after they straying into its territory.
Their relationship is open to interpretation, but it appears that both of them tend to be reluctant to show their feelings several times. Nanachi proclaimed annoyance at Reg's cries over Riko, while the feeling was actually pity, and Reg freaked out whenever he assumed that the former messed up at healing Riko, but still aiding at finding medicine. Their relationship seems awkward, with Reg getting confused and angry at Nanachi's sarcasm with the latter getting uncomfortable every time he came close.
This ends when Reg reveals his incinerator, a device capable of permanently injuring Mitty. Nanachi realizes this, and asks Reg to kill her while opening up about their past, being calmer this time and even giving him time to think. Reg too feels pity and vows that he'll do that as long as Nanachi would not commit suicide afterwards, and if the latter accompanies them on the journey.
Nanachi still doesn't like being touched by him, saying the way he does it is "too lewd," but values and trusts Reg as a friend and comrade.
Nanachi has demonstrated advanced tracking and stalking skills; when Reg and Riko first entered the Abyss' 4th Layer, although Reg could tell that Nanachi was nearby, he was unable to pinpoint their location. They were capable of tracking Reg and Riko throughout their journey in the 4th layer, continuing to remain hidden, until they voluntarily revealed themselves upon seeing Reg scream when he thought that Riko had died.
On top of top-notch tracking and stalking skills, since becoming a Narehate, Nanachi has been able to see the flow of the Curse of the Abyss — a mysterious force that is behind the ailments human beings suffers upon attempting to ascend from the Abyss. Thus, they are capable of avoiding it.
Aside from htheir skills granted to her/him by their Narehate nature, Nanachi has been shown to be deeply knowledgeable about the flora and fauna within the abyss; they are capable of determining what is edible, as well as if something has any medicinal properties. Their time spent in Idofront has also lead to them knowing how to perform some complex surgeries. Using this knowledge, Nanachi has tended to myriads of maladies that delvers may suffer from, such as being able to splint broken arms, suture open wounds, and even creating an antidote for Tamaugachi venom. Many of the curative methods and medicines they use are unknown even to delvers, who are often thought of to be the most knowledgeable of the Abyss.
Nanachi is also shown to be artistically talented, having demonstrated excellent ability in drawing. They have drawn pictures of themselves, Mitty, Reg, and Riko; a representation of how the curse works for Reg; and accurate depictions of the things they required Reg to fetch in order to aid them in healing Riko's arm.
- Nanachi is generally presumed to be female, based upon their feminine appearance. However, their gender and sex have never been explicitly stated within the series itself. The only gender referent used by Nanachi is the pronouns that they used to refer to themselves with. When talking about themselves, Nanachi uses the pronoun oira (おいら, which is similar to ore (おれ) but more casual. Evokes a person with a rural background, a "country bumpkin"), which has a masculine connotation to it. The creator of Made in Abyss, Akihito Tsukushi, commented on Nanachi's sex on Twitter, stating: "the sex of Nanachi is unknown. Let's imagine :)." The official English translator of Made in Abyss has also chosen to use gender neutral pronouns.
- Occasionally there are extra pages at the end of chapters that give more detailed descriptions of the creatures and relics seen; Nanachi often shows up on these pages giving their own insight on the subject. These small bits are called "Nanachi's Trivia."
- Nanachi has an "irresistible fragrance". In particular, the base of their tail smells really good. They are also really fluffy. This is an interesting parallel between her former human self, who was smelly and repulsive to others.
- Their age is likely older than appearance suggests.
- When signing their name, they always draw a picture of their face with the characters for "Nanachi" underneath.
- Nanachi makes a brief cameo on Pop Team Epic's episode 2 when (s)he appears on one of Popuko and Pipimi's "Ridiculous Fortunes." It says "Good Luck, Nanachi is cute!"