After Mantine Surfing from Big Wave Beach, you reach Heahea Beach and start looking for Lillie and Professor Kukui.
Arrival on Heahea Beach
At the beach, Hau will tell you to look for Lillie and Professor Kukui. You might earn some Beach Points depending on your Mantine Surf score.
Go to the far left side of the beach to find a bottle with a letter and a Heart Scale in it. Read the letter and it will ask you to look for someone on this island who loves dancing and Corsola.
Go to the northeast corner of the beach to find a Soda Pop.
Go southeast from the beach to reach Heahea City.
Go south in Heahea City and you will find Lillie and the Professor. You will meet Olivia and Mallow as well.
Go into the Ferry Terminal and talk to the people in the upper-left corner to get a Premier Ball.
In the Tourist Bureau, the Gentleman there is the Name Rater. He can change the names of pokémon that you caught.
When you approach the apparel shop, there will be a cutscene. Lillie asks you to meet her in Tide Song Hotel.
In the apparel shop, a Beauty will ask you to catch a Salazzle, then show her your Pokédex. She will pay you if you do.
Talk to the woman south of the apparel shop to get a Rare Candy.
Go a little farther down the street and you will find a Pokémon Center to the right. After visiting the Pokémon Center, go outside and go upward toward the hotel where Lillie went. Keep going toward the hotel until two people stop you. Dexio challenges you to a battle. Pokémon Trainer Dexio has a level 15 Mime Jr. and a level 15 Espeon. You get 2100 Pokédollars for winning.
Afterward, Dexio heals your pokémon and gives you a Full Restore.
Go toward the entrance of Tide Song Hotel and talk to the bellhop, and ask him what is wrong. He will tell you his story.
Go into the Tide Song Hotel and talk to the Dancer near the elevator. If you found her letter on Heahea Beach, she gives you a Heart Scale.
Talk to the man behind the counter in the lobby. If you talked to the bellhop outside, you will tell him about it. The gentleman will then ask you to catch a Magmar and show it to the bellhop.
Then when you are ready, go south from the hotel, then east to enter Route 4.