As the Trial Captains and Kahunas are somewhat like the equivalents of Gym Leaders in Alola, this makes Nanu the first leader specializing in Dark-Type Pokémon outside of Elite Four.This may have a relationship to him being a Dark-type trainer, and being mostly seen at night, as albinos are very sensitive to light.Nanu may have some form of albinism, as he has very light skin, pale hair, and telltale red eyes.Nanu is apparently an old acquaintance of Looker, and even refers to an incident where he witnessed a previous partner of Looker devoured by the Ultra Beast Guzzlord.Nanu's VS sprite in Sun & Moon Pokémon Sun and Moon Please help the Pokémon Wiki by expanding it. He helps the player character, Annabel, and Looker catch the ultra beasts and even challenges the player character to another battle. He comes to the player character's party after the champion is beat. Later, he challenges the player character to a battle, saying he's the kahuna.
Nanu eventually runs into the player character where he is mildly shocked to hear they are going to save a Pokémon (a young girl's from Po Town) and allows the player character inside Po Town despite knowing the full risks. However, Nanu didn't believe he had the time to deal with them and allows the gang to take over Po Town. Later, Nanu joined the police force and worked close by Team Skull simply because the rent was low as most people rather avoid Team Skull.
Even despite his lazy personality, Nanu couldn't turn down the offer chosen by one of Alola's Tapus. Nanu lives on Ula'ula Island where he was chosen as the Kahuna by Tapu Bulu. He also lightens up more by the end of the main story congratulating the player character for becoming a Champion. However, once he has had a good battle or something amuses him, he will crack a small grin. Although he accepted to be a Kahuna since he was chosen to be it, he turned down the offer to be in the Elite Four simply because he had a choice to decline and allowed his niece Acerola to take the role instead.
He is also rather lazy as he allowed Team Skull to take over Po Town as he feels he has no time to mess with them. Nanu, overall, is a rather gloomy and cynical character who rarely sees the brighter side of things. He wears long black pants with sandals and is also seen wearing a necklace with Darkinium Z on it. He also wears a burgundy shirt with a black jacket on it that has two yellow emblems on the sides (presumably to indicate that he is a police officer). Nanu is an older man with gray hair, red eyes, and thick eyebrows.