Having seen off Ida and Kanoa, Ash and his classmates return to the Pokémon Center for a breakfast prepared by Mallow. Rotom announces that Lana and Sophocles have achieved their goals for their research projects, and encourages everyone else to do their best. Like Ash, Kiawe declares that he wants to battle Tapu Fini to prove his skills. Ash then invites Kiawe to join him in the search for the guardian deity. Kiawe adds that they will first have to pay their respects at the Ruins of Hope.
Later, Mallow, Lillie, and Sophocles visit Hapu at her home. Mallow presents Hapu with an array of food made from Hapu's own Poni Island radishes. Hapu agrees to taste test the cooking after Mallow explains that she hopes to put the Poni radish dishes on her family's restaurant menu. Before she digs in, Hapu confesses that radishes taste best when they are unprocessed, and she offers Sophocles a fresh radish to prove her point.
Meanwhile, Ash and Kiawe make their way through Poni Breaker Coast and towards the island ruins. This soon turns into a speed walking competition followed by a foot race. The pair soon reach the finish line, a large rock, at the same time. Rotom goes on to verify that the two boys did in fact tie. The pair then reach the entrance to the Ruins of Hope, however the ruins are submerged by the high tide. Kiawe begins to pray in an attempt to get Tapu Fini's attention, but he is interrupted by Ash's direct battle challenge. Ash then offers Kiawe a battle, and explains that Tapu Fini appeared during his match against Gladion the other day. Kiawe is pumped and challenges Ash to a heated Double Battle. Elsewhere, Lana continues training her Pokémon. Lana has Brionne make a large enough water balloon that she and Sandy are able to enter it. The bubble soon fails, so Lana has Brionne continue to practice. Over at Hapu's house, Hapu is amazed by the deliciousness of Mallow's simmered radish. Before she takes another bite, Hapu declares that she has more work to perform, so Mallow and the others offer their assistance.
Ash and Kiawe begin their Double Battle. Ash commands Pikachu to use Quick Attack on Kiawe's Turtonator and orders Torracat to strike Marowak with a Fire Fang. Turtonator and Marowak counter with Dragon Tail and Iron Head respectively. Ash has Pikachu ensnare Kiawe's Pokémon in an Electroweb. Turtonator, however, uses Shell Trap to escape the Electroweb and evades Torracat's Flame Charge. Pikachu manages to intercept Marowak's Bonemerang with Thunderbolt. Torracat attempts to attack Turtonator with an Ember attack, but the move is soon overwhelmed by Turtonator's Flamethrower which also sends Torracat into a nearby cliff. Torracat bounces back and lands at Ash's feet seemingly uninjured. Ash then orders Torracat to use Revenge as Pikachu goes in for an Iron Tail. Turtonator swivels its back towards Torracat and uses Shell Trap to repel it. Pikachu's Iron Tail then collides with Marowak's Shadow Bone to a detonating effect. The two pause the battle to admire each other's strength, but then a mysterious mist rolls in. The pair decide to investigate, and soon Ash shouts out in shock at something. Meanwhile, Hapu shows Sophocles and the others how to harvest Poni radish. She informs the group that because of their long shape, Poni radishes must be pulled upwards to avoid breaking them. As instructed, Vikavolt harvests a radish without any trouble.
Kiawe soon finds his Pokémon and Ash trapped in an odd blue sphere. He attempts to barge his way through, but is repelled several times. Soon, Tapu Fini and an old man, Sofu, appear. Sofu scolds Kiawe for harming the sacred ground around the Ruins of Hope. Ash and Kiawe attempt to explain themselves, but neither Tapu Fini nor Sofu are accepting of their excuses. Tapu Fini sends out a beam of water to Kiawe, and gives him a water clock on his wrist. Sofu instructs Kiawe to collect scales from Tapu Lele in order to quell Tapu Fini's rage. The catch, however, is that when the water in the water clock has all moved to the other side the time is up and Ash and the others will suffer the consequences for their sins. Kiawe realizes the scope of the situation and accepts its difficult conditions. He then calls out his Charizard to fly him to Akala Island, the location of Tapu Lele.
Back on the Ancient Poni Path, Hapu admits that all of Mallow's cooking was delicious. Mallow is pleased by Hapu’s review, then asks if she knows any traditional Poni cuisine. Under Hapu's instruction, Mallow goes on to cook up a dish of fluffy radish, a dish that Hapu's grandfather used to prepare for Hapu. Hapu is pleasantly surprised and the small fritters instantly remind her of her childhood.
Kiawe soon lands at the Akala Island trial site and calls out to Tapu Lele. The guardian deity appears and uses Psychic Terrain to control the situation. Tapu Lele challenges Charizard to a battle, and Kiawe accepts the challenge. Charizard's Flamethrower is dispersed by Tapu Lele's Dazzling Gleam. As Charizard approaches with a Slash attack, Tapu Lele blocks its opponent's attack and send it towards the ground. While Charizard manages to break its fall with a Fire Punch, Tapu Lele forces Charizard into a nearby cliff. The resulting collision sends a large block towards Kiawe, but Charizard manages to recover and rescues Kiawe. Charizard then soars into the air as Tapu Lele giggles and maniacally uses Dazzling Gleam. As Charizard ascends into a sharp climb, one of the Dazzling Gleam attacks clips its wing and Charizard begins to fall. Kiawe then remembers a time when he was training alongside his grandfather. He and his grandfather rode on Charizard, and just before they hit Wela Volcano, Kiawe's grandfather ordered Charizard to use Aerial Ace to begin a new ascent. With his grandfather's advice in mind, Kiawe orders Charizard to use Aerial Ace, and the pair narrowly avoid hitting the ground and return to a sharp climb into the sky. The maneuver forces Tapu Lele to have to withdraw into its protective shell to avoid its own Dazzling Gleam attacks. The strategy impresses Tapu Lele, and the island guardian gives Kiawe some of its scales before twirling away.
Back at Poni Breaker Coast, Ash and the Pokémon are released from their orb prison. Sofu tells Ash that they're free to go, under the condition that Kiawe takes their place. He then adds that Kiawe abandoned them and will not return. Ash rebukes Sofu's claims and decides to stay put while he waits for Kiawe to return. Kiawe manages to make landfall just as Charizard collapses from its exhaustive efforts. He makes a run towards the Ruins of Hope, fully aware that the water clock is running out of time.
Over at Hapu's, Lillie and the others thank Hapu for her hospitality and they promise to catch up again soon. As the trio leaves, Hapu calls out her Golurk and Mudsdale, though she declines to admit that she was simply feeling lonely. Later, Kiawe wills himself to overcome his limits and he reaches Tapu Fini in time to deliver Tapu Lele's scales Pokemon and Ash are happy to see Kiawe, and Sofu declares that Kiawe barely made it. Tapu Fini waves its arms in the air, causing Charizard to emerge from its Poké Ball. The island guardian then uses the retrieved scales to help Charizard recover, and the Fire type instantly feels the relief. Tapu Fini also gives Kiawe a Flyinium Z for his efforts. Sofu notes that Charizard knows Aerial Ace, he then adds that the Z Crystal will help Charizard to truly spread its wings. Kiawe is curious as to how the old man knows about Charizard's Aerial Ace, but the old man simply dismisses Kiawe's query. Kiawe and Charizard go on to perform Supersonic Skystrike. Rotom, wearing its Detective Laki wig, deduces that the day's events were likely a trial set up for Kiawe by Tapu Fini. Ash and Kiawe look around and quickly notice that the fog has faded, and both Tapu Fini and the old man have vanished into thin air. Sofu and his old friend, Kiawe's grandfather, look down on Kiawe and Ash from a cliff and smile before vanishing into the ether.