Ash, his classmates, and his old friends Misty and Brock have a picnic lunch, prepared by Brock, by the sea. Brock admits that Kiawe's family's cheese was the special ingredient, and Kiawe explains that his family's cheese is the best on Akala Island. With the mention of Akala, Brock takes out his blue book and flips to his pages on Olivia, much to the disapproval of Misty and Lana. Brock then declares that they will visit Kiawe's farm, secretly hoping to catch Olivia during the visit. Kiawe explains that Olivia travels a lot and may not be there, but Brock suggests it will then be a fateful encounter. The group then sets off for Akala Island aboard their Ultra Guardian Ride Pokémon.
During the voyage, Lana decides to call out Sandy and Popplio to enjoy a swim. As the two Pokémon play in the water, Psyduck comes out unprompted, but Misty quickly recalls it to its Poké Ball, as it can't swim. On a nearby island, Meowth spots the group traveling to Akala Island through his binoculars and alerts Jessie. She declares that they must catch Pikachu for Giovanni, but Meowth explains that they still need to fix their mecha. Jessie shouts at James and Wobbuffet to get the machine working faster.
Ash and his friends arrive at Kiawe's family farm, and Misty and Brock explore the area. After they get into some misadventures, the Miltank and Mudbray's cries alert Kiawe and the others to an intruder, a wild Kangaskhan. As Kiawe is about to send out one of his Pokémon to fend off Kangaskhan, Brock alerts everyone to Kangaskhan's empty pouch. Sophocles spots the baby Kangaskhan hiding behind its mother's leg, and Brock notices it has a swollen leg. Brock approaches the Kangaskhan duo, pulls out a Poké Ball, and calls out his Comfey. Ash is surprised to see that Brock now has a Comfey, and Brock explains that Nurse Joy gave it to him as thanks for his earlier assistance. Brock continues to approach, and his calm tone and Comfey's moves help calm the aggressive mother. Brock eventually reaches the injured infant and goes on to treat her injured leg. With her leg now bandaged, the baby Kangaskhan climbs back into her mother's pouch, and the duo then returns to the wild. Just as everyone is admiring Brock's professionalism and skills as a Doctor, Brock's attention returns to meeting Olivia.
The group decide to ascend Wela Volcano in the hopes of meeting Olivia, but Brock is increasingly becoming frantic and emotional as the search goes on. Olivia soon spots the group and rushes towards them, tripping on a stone in the process. Brock reaches out for Olivia's hand and formally introduces himself to her and then proposes that they get married. As Brock explains that their meeting was fate, Misty pulls him away by the ear and explains that Brock had actively searched for Olivia. Everyone continues to trek up the volcano, and Olivia explains that she has more important island kahuna duties to attend. Mallow requests a photo with the island kahuna and Olivia agrees. Everyone poses and Rotom takes the snapshot, but when Rotom reveals the photo, it also includes a familiar trio of Hikers. Olivia explains that the Hikers now patrol Wela Volcano Park, though they have a bad habit of photobombing sightseers' holiday snaps. Brock looks over the photo and is irritated to notice that one of the Hikers' heads is covering up his face. The trio of Hikers soon leave the scene just as quickly as they arrived. As Brock enters an angry tirade, Kiawe tells Olivia that Brock is a battler and is the former Pewter City Gym Leader. Brock, with a glint in his eye, adds that he was a Rock-type specialist. Olivia is instantly interested and offers Brock a match, which he gladly accepts.
Brock sends out his faithful Sudowoodo to battle against Olivia's Lycanroc. Olivia makes the first move and has Lycanroc fire a Rock Slide. Sudowoodo swats the projectiles away with a Hammer Arm. Olivia is impressed by Brock's performance and has Lycanroc use Double Team followed by Accelerock. Sudowoodo uses Feint Attack to quickly locate the real Lycanroc amongst its duplicates and manages to land a blow. Lycanroc retaliates with Drill Run, but Sudowoodo is still standing. Olivia is astounded by Sudowoodo's resilience and asks Brock to show her more of his techniques.
Meanwhile, Team Rocket uses the opportunity to grab some of the group's Pokémon and everybody on the scene with their Giga Meowthbot 4. Team Rocket launch into their motto and soon try to leave the area. However, Olivia's Lycarnoc hits the mecha with a Rock Slide from behind. Brock has Sudowoodo strike the robot with a Low Kick, immediately infuriating the Rocket trio. As Meowth attempts to fire a powerful beam from the mecha's head, Olivia prepares to use a Z-Move to deal with the troublemakers. Brock grabs a hold of Olivia’s hand, and together the pair pass on the Z-Power to Lycanroc to perform Continental Crush. The attack is unusually love heart-shaped, but Meowth manages to hold off the attack. Suddenly Stufful and its mother Bewear arrive on the scene. The distraction causes Meowth to lose focus and the mecha is slowly crushed by Continental Crush. The Pokémon are immediately freed, and Pikachu uses Iron Tail to free Ash and his friends. Eventually, the mecha explodes, but Bewear manages to rescue Team Rocket from another blast off and flees Wela Volcano.
Back on Melemele Island, Ash, his friends and Olivia join Professor Kukui and Professor Burnet to watch some fireworks. Misty and Brock thank Ash and declare their Alola vacation an unforgettable time. Ash declares that he will continue to study Pokémon in the hopes of achieving his dreams of becoming a Pokémon Master. Misty and Brock are not surprised by Ash's ambition, declaring they know each other too well after such a long time. Misty then declares her dream is to continue training Water Pokémon and to make Cerulean Gym the world's best Gym. Misty and Ash then agree to a Gym challenge the next time they meet. Brock, Misty, and Ash put their hands in a circle and lift them out in celebration.