Nai is an 8 years old girl, composite Esper capable of using both Metamorphosis and Teleportation using shadows to relocate herself, and who also posses some sort of sensory ability allowing her to do everyday tasks despite keeping her eyes covered.
While she is in her human form Nai is always disheveled, with her hair pulled back only by a large band on her head that she uses to cover her foreheand and eyes.
While in her cat form she appears to be a black kitten with slightly ruffled fur.
Originally she only weared a black and white dress with two large flowers on her chest, later she started using a ninja themed suit for missions, and other varios dresses.
As the child she is, Nai is somehow naive and obedient, she was put in charge to watch over Yuri Kumoi, disguising herself as a little black kitten while the personalty of Yuri is present, being allowed to keep her human form in fornt of Mirage, Phantom Daughter, or whenever she is alone.
Comically, spending lots of time as a kitten have led her to actually behave like a cat, acquiring a taste for canned cat food, talking in Cats language, feeling hunting instincts towards animals like fish, and a desire to use a little cat door Yuri set in the appartment door.
Nai's teleportation ability uses shadows as a catalyst, using the shadows as portals Nai is freely able to travel between them.
Nai often takes on the form of a black cat and follows Yuuri around. She has also been shown to transform parts of her body into a shadow-like form
Yuuri Kumoi: Nai is in charge of taking care of her, but having to keep in a kitten form it ends up being the opposite, Nai bevahes like Yuri's beloved pet, both love themselves, so much that after the combining of Yur's personalities Nai follows her even in her auto imposed exile.
Hanzo: After the ninja was adopted by Mirage and hid in the house of Yuri, Nai started to trat him as his older brother, and both of them became a ninja themed team who fight together to accomplish missions for Phantom Daughter or Mirage.
- Nai's name literally means "nothing".
- Zettai Karen Children Chapter 186 Page 11