Alolan Pokémon League

In Alola, the Elite Four consists of four strong trainers, such as the former Trial Captains Acerola as well as Molayne, Olivia and Kahili. The champion is Kukui.

Before Nanu's Revenge
Before the League was formed, Trial Captains and Kahunas would battle trial goers on the summit of Mount Lanakila. This was started to be considered dangerous and Kukui decided to start building a structure, although it remains uncompleted for the time being, as the weather on top of the summit is unpredictable.

According to Nanu, he was asked to become part of the E4, but gave the roll to Acerola instead, as she was becoming too old to be a Trial Captain and he didn't want her to be disappointed, too.