Kurusu was captured by a trainer resembling that guy who shows Gold/Kris how to catch Pokémon in Generation II. He was soon after taken by a Mew for unknown reasons, and dropped onto the titular Lost Island. After following a Butterfree into the depths of a woodland, he befriended a Caterpie almost instantly. Then, a storm hit. Kurusu and Caterpie ran for cover, only to somehow enrage a Venusaur, who chased them to a cliff. Caterpie used String Shot to trap the Venusaur, and then Kurusu pushed it over the cliff.
Later, while exploring, Kurusu and Caterpie come upon a house. They then arrive at a beach, where the same Venusaur that attacked them earlier pops out of the water, only to be blasted away by a Blastoise. Kurusu then takes notice of a Honoguma on the opposite shore.