Mitty

About
Mitty is an amorphous Narehate that lives with Nanachi on the 4th Layer of The Abyss. Mitty used be a regular human girl in the past, and her current appearance is the result of the ascension from the 6th layer.

Appearance
As a human, Mitty was an upbeat and positive human girl. She was almost always smiling and aspired to be "a future white whistle." Her hair was dark in color, and long and messy, sticking out at random angles. Some of it seemed to be tied up into a messy ponytail on the back of her head.

Personality
Before becoming severely malformed, Mitty wanted to become a White Whistle. She very upbeat and positive, wondered endlessly at the world around her, and always tried to look on the bright side of things, even when Nanachi was often negative. She was very outgoing, as she was the one who first approached Nanachi and insisted on being friends and partners. After becoming a Narehate, her intelligence was vanished, and she cannot communicate anymore with Nanachi. All she was able to do was make soft noises and crawl around a bit. During Bondrewd's testing and Nanachi's attempts to kill her, she would cry as a reflex, but likely didn't feel any physical sensation or emotion, as Nanachi said "Mitty's soul was trapped inside" within her narehate form.

Mitty's Possible Reincarnation
As Reg incinerates Mitty he says "may your soul cycle again". Afterwards, Riko wakes up from her dream and recalls that there was a "smoke scent" and she saw a person much like Mitty stand up and leave. Nanachi references the idea of a rebirth several times: Reg's incinerator is said to rewrite the rules of the Abyss. It doesn't seem implausible that the incinerator returned Mitty's soul to somewhere in the Abyss. It is also possible that the people in the Capital of the Unreturned are trying to trick Nanachi, so the exact answer is currently unknown.
 * "Mitty.. we'll meet again soon" Chapter 24, Page 8
 * "If I just ditch you halfway, [Mitty] will chew me out the next time we meet" Chapter 26
 * "The next time I meet Mitty... I might need to make her some food..." Chapter 28 Page 9
 * Riko: "It's too early to give up. This is the Abyss after all! We'll find a way to meet Mitty once more."
 * "Mitty, the warm bundle of curse that the masked man left behind..." Chapter 42 Page 12

Immortality:
After becoming a Narehate, Mitty was resistant to every form of Bondrewd's torture and experimentation. She's had stakes driven through her and limbs chopped off, but has healed every time, with limbs even growing back in place of those that were lost and also can neutralize/remove any kind of poison with herself. Nanachi tried everything she could to put her out of her misery during their time together. In the end, the only thing that was ultimately able to kill her was Reg's Incinerator.