Sun is a courier, he is Pokédex holder. He is the male playable character in Pokémon Sun and Moon, His first appearance is in Pokémon Special Sun and Moon.
Sun was the beach of Alola city doing his job "Pyukumuku chucking" when he trows accidentally a pyukumuku at Moon, she demands a compensation for her clothes.
She asked why is he doing that job and he tell her that he gotta save a 100 million yen as soon as posible, then two guys arrived where he was to examine if he did his job correctly, but thaey find another pyukumuku in the sand and decided not to pay him, but offer him to do this job of the rest of his life with only 10 percent of what they agree. Moon told him to refuse cause she saw one of them drop a puykumuku in the sand, one of their pokemon attacked her and he decided to fight against them.
She asked him what is the reason of the 100 million yen but he said it's a secret, then he offer her to do the delivery she needed to do.