Hayako Sakurai is a brilliant Japanese scientist and one of the main characters in Endless Ocean 2. She is a renowned marine scientist known for her broad knowledge of various different complex fields of study.
"Hayako comes from a well-known family in Kyoto, and her ferocious intellect has allowed her to earn PhDs in such disparate fields as mechanical engineering, ecology, marine veterinary science, and archaeology, even though she is only in her early 30s. Like many geniuses, she tends to jump from one topic to another and can be a little too candid, which tends to make others a bit uncomfortable. She also loves celebrity gossip."
"Hayako is a highly educated scientist with a wealth of knowledge about the ancient Okeanos civilization. She’ll prove invaluable to the L&L; Diving Service once they ramp up their search for clues to the whereabouts of the Okeanos’ Pacifica Treasure."
She befriends GG, Oceana and Jean-Eric Louvier during the story, and develops a strong friendship with the player. She advises him or her with their dolphin training, assessing the dolphin partners to monitor their progress. Passing her assessments allows the player to teach his or her dolphins more advanced tricks, while also unlocking the ability to accept dolphin show requests.
Hayako is depicted as a rather mature, calm and collected woman with a slight sense of humor. She is the only major character in the game to not show visible distress, and her down-to-earth nature allows her to act as the voice of reason during group discussions.
Highly intelligent, Hayako is a highly educated oceanographer. She knows all about most known marine life, and is often the one to point out fun facts about various species. Befitting her occupation, she is always studying animals and looking for new ways to answer scientific questions. She is also an experienced diver and even knows many ancient languages, which proves useful in finding the Pacifica Treasure.
According to Jean-Eric, Hayako eats a lot. While dolphin training, Hayako sits on the deck with GG and eats what seems to be a bag of potato chips. Those same chips appear during the Voice of the Night Sky quest cutscenes, assuming said cutscenes occur after she joins the team. She further hints at her love of food when the player shows her the giant grouper and Amazonian manatee, making note of how discussing the former's diet makes her hungry, and how the plants consumed by the latter don't make good salads.
When diving with Hayako, she grants the ability to locate and name any creature within nearby map tiles. The name of creatures is shown and any place the creature is located will be represented by a small red dot. Any creature that is not registered in the Marine Encyclopedia will be named ???. This ability does not, however, allow the player to find any creatures under zoom-mode glow spots. She can also let you see any scenes that you have unlocked in that area.