Island Kahuna

Kahuna's are individuals chosen by Alola's island deities to govern the islands of Alola.

Description
From Pokémon Sun and Moon official website:

Each of Alola’s four islands has a leader, called the island kahuna, who governs the island. Kahunas are chosen by the Pokémon known as guardian deities, which are also found on each island.

Known Kaunas

 * Hau- guards your home island