Chloe and Eevee are on their way home from school when suddenly, Ash and Goh appear behind her. They're chasing after a Shiny Voltorb and ask Chloe to stop it. Panicking, she tries to do something. As the Voltorb tries to jump over Chloe, Goh takes the chance and catches it from mid-jump. He lets it back out while Ash explains to Chloe that Shiny Pokémon are rather rare. Suddenly, a Trainer and his Dewott rush in and enthusiastically hug Voltorb, who promptly Self-Destructs. The Trainer apologizes and introduces himself as Gorman, a "blue Pokémon fanatic" from Kalos. He invites the three to participate in various activities related to blue Pokémon called "Do-Blue". Ash and Goh agree, and while Chloe remains hesitant, Eevee eagerly agrees, reluctantly pulling her in too. Along the way to the first Do-Blue activity, the Do-Blue group passes by a disguised Team Rocket, who overhear Gorman talking about Pokémon fanatics. Deciding to make some money by exploiting his enthusiasm, they start scheming.
Gorman first leads the Do-Blue group to a museum that's holding a display of photos featuring various blue Pokémon. He draws their attention to a picture of a Brionne and starts theorizing what its expression in the image means. He theorizes that it's on a quest to find out why it dances, launching into a fantasy of him meeting Brionne and bonding with it, so he can take part in its dances. Suddenly, another blue Pokémon fanatic, named Bluto, along with his partner Meowstic, appears and calls Gorman a simpleton. His personal theory is that Brionne was perhaps driven out of its home by a brutish Pokémon, and launches into his own fantasy of training with Brionne until it evolves into Primarina. Gorman protests this fantasy, disliking the shade of blue on Primarina. Just then, Team Rocket appears, disguised as blue Pokémon enthusiasts, and presents them their Wobbuffet. Gorman and Bluto are excited, and Jessie offers to take pictures of them with Wobbuffet, but the Patient Pokémon gets creeped out by the two Pokémon fanatics and runs off, with the rest of Team Rocket giving chase. Bluto then notices Goh's Voltorb and hugs it, causing it to explode yet again.
Later, Gorman expresses the frustration he's now feeling due to his encounter with Bluto, which wasn't the first time the two enthusiasts have met. Still, he decides to push it aside and lead the trio somewhere else to continue with their activities. Meanwhile, Team Rocket has caught up with Wobbuffet. Meowth translates that Wobbuffet is feeling scared, and although the Rocket trio tries to calm him down, he promptly grabs his Poké Ball and recalls himself, much to the trio's surprise.
The next destination on Gorman's tour is a café, which is decorated with blue surfaces and serves blue food and drinks. It soon turns out, however, that Bluto is nearby again, enjoying blue pancakes made of Yache Berries and covered with Oran cream. Gorman counters by presenting a baked toast covered in Rawst and Kelpsy juice. The two blue Pokémon fanatics fiercely eat their respective dishes while Ash, Goh, and Chloe look on. Afterward, Gorman is dismayed that he ate so fast that he didn't have time to memorize the taste.
Next, Gorman shows the trio a commercial for a blue candy, featuring a Vanillite and a Frogadier, and takes them to the spot where the commercial was filmed, which he considers practically sacred. Unsurprisingly by now, Bluto appears again and starts arguing with Gorman, claiming that Vanillite isn't blue at all, but white. Their argument is interrupted when the disguised Team Rocket reappears, with Meowth disguised as Wobbuffet. At first, the Pokémon fanatics are excited, but soon start getting suspicious. Meowth attempts to imitate Wobbuffet in order to look more convincing, but ends up falling over, causing his disguise to start falling off. Seeing this, the Rocket trio beats a hasty retreat to avoid being completely exposed.
Gorman and Bluto start accusing each other of ruining their respective experiences, while Goh wonders why the two keep showing up in the same places. Chloe realizes that since they're both blue Pokémon fanatics, they must've ended up making identical plans. This is soon proven correct, as both Gorman and Bluto receive notifications of a plushie giveaway for the blue candy's fifth-year anniversary. Both of them rush to the local Poké Mart to obtain the plushie, but only one is currently available. As they argue over it and each of them tries to claim it for themselves, they end up ripping the plushie in half. This angers both of them so much that they finally decide to settle their differences, with the loser having to return to Kalos.
The two Pokémon fanatics confront each other and blindfold themselves, before sending out two Pokémon each. Ash wonders if it's a Double Battle, but surprisingly, instead of attacking each other, the Pokémon walk up to the opposing Trainer and are touched by them. Goh figures that this could be a similar competition as having to recognize what food you're eating without looking at it, which is proven correct as Bluto correctly identifies Gorman's Pokémon as Nidorina and Phanpy, while Gorman manages to correctly guess that Bluto's Pokémon are Seismitoad and Croagunk, with both of them also being able to tell what hue of blue they are. Before they can continue, however, Team Rocket appears again, snatching Pikachu, Eevee, and Grookey in a net. James aims a net gun at the Pokémon fanatics' Pokémon, but before he can fire, Bluto has Meowstic use Disarming Voice, causing James to drop the net gun, while Dewott uses its shells to cut the net containing Pikachu, Eevee, and Grookey, freeing them. Meowstic then brings the Rocket trio's balloon down to the ground. Frustrated, the trio calls out to Pelipper. Pelipper appears, but before it can drop the Rocket Prize Master, it gets freaked out by the Pokémon fanatics obsessing over its blue color and performs a U-turn, flying away again. With the Rocket trio left defenseless, Ash promptly has Pikachu deliver them the usual blast-off Thunderbolt.
Just as the crisis has been dealt with, Gorman and Bluto's phones notify them of a launch event for a new candy in the next town over, so they rush off to attend it. Ash, Goh, and Chloe wonder if they're friends now after they just fought side by side, but regardless, they laugh the entire thing off.