Nai is the main character of the story.
Nai has short, white hair. The two tips from his hair, which are sticking out above his ears are lavender. It's confirmed that Nai is an animal, a Niji. However he is only part Niji and he was mad that way by Karoku.
Nai is a sweet kid but is quite naïve. When Gareki first found him, he did not know what blood was. He is very trusting and kind, this is shown several times throughout the series.
He claims to have always been living with a man named Karoku in a forest near Karasuna. When Karoku does not appear one day, Nai ventures outside and finds a trail of blood leading from their home to the sea, and a left-behind bracelet (Circus I.D.).
Gareki and Nai have a very close relationship, both showing great care and concern for each other. This is shown when Gareki provides and protect Nai even though he had just met him. Nai also shows that he cares for Gareki when he tries to distance himself from Gareki because Karoku said, "You don't want him to break do you?" frightening Nai very much. However this was later resolved and Gareki and Nai are able to become close again.
Yogi and Nai are good freinds, due to Yogi's childish and bubbly personality he makes a wonderful playmate for Nai. Yogi also protects Nai many times from atack.
- His name means Nothing or Not existing.