While playing outside his house, Kirby is chasing butterflies, and spots a strange frog. They talk to each other, and Tiff and her little brother Tuff arrive to see him and tell him that Hana needs help with her laundry. Kirby follows.
Devil Kirby makes his first strike at the Mayor's house by wrecking Hana's laundry, and she calls for help. Nobody can believe it, but this escalates to Devil Kirby, in a nihilistic manner, destroying Curio's shop, smashing Tuggle Tago's store, spraypainting Hana's friend's house, and then heading to a building where fortune teller Mabel is, where the fiend smashes her crystal ball so she cannot tell fortunes. Having become even more nihilistic, Devil Kirby steals the Mayor's car (Mayor Len even runs after his car and protests that Kirby does not have a learner's permit.) smashes the gas station Gus Gasu was running.
King Dedede notices what is going on and believes that he should be the one who is best at what he does best: causing havoc to his people. Escargon tells him to be at least happy that the Cappies are miserable.
Devil Kirby then trashes Chef Kawasaki's restaurant and, continuing his nihilistic streak, sets the restaurant on fire as King Dedede confronts him. Chef Kawasaki cries over his restaurant. ("My Restaurant!!!")
At night, as the Cappies are in a panic, King Dedede summons the Nightmare Enterprises salesman. They discuss what happened. The salesman at first cannot believe his ears ("But Kirby's a good guy!"), but finally concludes that the Devil Frog is responsible, being able to multiply his target's malice by at least a million. Tiff, Tuff, and Meta Knight hear this out and decide they must have the Devil Frog leave Kirby's brain. King Dedede and Escargon order the Devil Frog's enemy, the Heavy Anaconda, knowing that it can destroy the Devil Frog. The Waddle Doo general pops in and warns his king that Kirby is destroying the castle. Tiff, Tuff, and Meta Knight exorcise the Devil Frog after Kirby bashes the Waddle Doo general, but King Dedede grabs the frog and attaches him to the back of his own head, turning into Buff Dedede. The Heavy Anaconda arrives and eats the Devil Frog and King Dedede, and the Devil Frog is destroyed. Kirby defeats the Heavy Anaconda via a torch Meta Knight had in his hands. Kirby uses his Burning and Fireball Spin to destroy the huge snake and save the king. Meta Knight closes the episode by explaining that the only time Kirby gets truly angry is when the justice of the universe has been crushed, and then hints toward a more powerful enemy.
- King Dedede and the Nightmare Enterprises Customer Service discuss what is happening:
- King Dedede: "Customer Service! Come here!"
- Nightmare Enterprises Customer Service: "Well, if it isn't the old D-meister! Your mood seems...!"
- King Dedede: "Tell me who's the baddest dude in Dream Land!"
- Nightmare Enterprises Customer Service: "Is that a trick question?"
- King Dedede: "You're supposed to say it's me!"
- Nightmare Enterprises Customer Service: "I'd agree with that!"
- King Dedede: "But those Cappies think it is Kirby!"
- Nightmare Enterprises Customer Service: "¡No! How come!?"
- King Dedede: "He smashed up Cappy Town!"
- Nightmare Enterprises Customer Service: "But Kirby is a Good Guy!"
- Escargon: "He's tearing up Cappy Town on a debris spree!"
- Nightmare Enterprises Customer Service: (Chuckles) "I'm betting it's that Devil Frog!"