Kayo is a character featured exclusively in Phantom Hourglass. He was Astrid's assistant and friend. When enemies came to the island, Kayo fought with outstanding bravery, but unfortunately had fallen to them. He was the only one with the knowledge on how to open the door in the basement of Astrid's house. After Link found the spirit of Kayo on the right side of the island, he learns the secret to opening said door. Kayo also later gives Link a hint of some nearby Treasure.
Kayo from Phantom Hourglass