Natsu Dragneel & Lucy Heartfilia vs. Hughes & Byro is a fight fought between Fairy Tail Mages Natsu Dragneel and Lucy Heartfilia, and the Royal Army Captain of the 3rd Magic War Division, Hughes, and the Chief of Staff of the Royal Army of Edolas, Byro.
Natsu Dragneel, Gray Fullbuster and Lucy Heartfilia go together in order to find Faust and save their friends. While Natsu and Gray bicker with each other as usual, Lucy begins to wonder about the Royal City's structure. She tells the two that she would not be surprised to find an amusement park in there and, sure enough, the three arrive in front of an amusement park. The three see Sugarboy riding the carousel when a ship suddenly falls on them. The group manages to dodge the ship and sees Hughes standing on top of it. The two sides then prepare to fight each other.
In the middle of their battle, Natsu is suddenly thrown on a roller coaster and gets very motion-sick. Lucy and Gray are rendered immobile when the ground underneath them melts and they get stuck. In order to help Natsu, Gray throws Lucy all the way up to Natsu while he uses Ice Make: Grappling Hook to get himself out of the melted ground. Lucy manages to grab hold of the coaster and reaches for Natsu. Hughes comments that Lucy is such a brave girl.
Lucy manages to reach Natsu on the roller coaster but gets frustrated when the safety belt won't unlock. Hughes waves his wand and the two whirl around rounded tracks of the roller coaster. The coaster leads them into water. Hughes laughs as he has a huge picture of Lucy, terrified and in tears, hugging a motion-sick Natsu on a board that says "Best Shot". As he laughs, he proclaims that Edolas Magic is wonderful and it's such a waste for it to disappear. Natsu is angered by Hughes' words and declares that it's not important whether people have Magic or not, they have lives. Lucy yells for Natsu to get down, takes advantage of the water and summons Aquarius. Unlike her usual self, Aquarius does not pick on Lucy and just prepares to attack. However, she becomes shocked when she realizes that she cannot control the water. Hughes tells them that everything in the theme park is his weapon. With the Command Tact, he uses the strong waves of the water to smash against them and send them away.
They end up in the Monster Academy. Natsu wakes up on some giant's hand and looks for Lucy, who's in a coffin-shaped box and is pleading for him to help her get out. When she gets out, she's in a Middle Eastern princess-like costume. According to the sign, it's the Method Actor Box. They see a dial and Lucy orders for Natsu to change her back. However, Natsu plays with it and dresses Lucy in a bunny suit, an aquatic suit and then a yukata. Later, Lucy is in a one-piece swimsuit with a waist floater. In irritation, Lucy dresses Natsu in the same outfits for revenge. When they hear Hughes' voice looking for them. Lucy orders for him to change her back to her real clothes because it's embarrassing. With a sinister look on his face, Natsu says he thinks it's fine and he just had a "great" idea.
Lucy changes into a bikini top and a mini skirt and attempts to seduce Hughes. However, Hughes does not even bat an eyelash and uses his Magic to have zombie-like monsters to attack Lucy. Natsu exclaims that the Sex Appeal Plan is completely useless. Hughes reveals that they're in the Monster Academy where the main attraction is the daily life of the students on campus. While Lucy complains about the monsters chasing her, Natsu sulks about her lack of sex appeal. Later, he stands up and tells Hughes that he'll attack him up front. Hughes replies that the Monster Academy's his favorite place and uses one of the monsters to cast Mummy Bandage that wraps Natsu around in bandages. Natsu burns off the bandages with his flames and attacks the mummy with it, surprising Hughes. He charges at Hughes with Fire Dragon's Claw and makes a direct hit. Hughes retaliates with Franken Knuckle that brings a huge monster and its huge fist down on him, also making a direct hit. It repeatedly strikes Natsu as he struggles to get up. Natsu manages to block the huge monster's hand and throws him over, surprising Hughes once more. Hughes orders the army of monsters chasing Lucy to take Natsu down and they comply, leaving Lucy alone. Natsu starts emanating with anger and Magic as the monsters halt in their tracks in fear. Hughes also notices this and gets very shocked when he sees Natsu in the form of a Dragon.
Lucy, still running although not being chased, suddenly bumps into an injured Coco holding a large key. Coco, in tears, pleads for Lucy to help her as a voice in the distance calls out Coco's name. Byro arrives and orders that the key be handed over. Lucy mistakes it as him asking for her Celestial Spirit Keys and she becomes alert. She tells Coco not to worry as she will defeat Byro.
She summons Taurus, surprising Byro and Coco. Byro calls Lucy's Magic "incomprehensible" as she "produced something from nothing". Lucy motions for Taurus to go and the bull charges at Byro with his axe but Byro dodges. Byro calls him impudent and casts Flame Liquid that defeats Taurus in an instant. He follows up with Storm Liquid that hits Lucy. When she regains her balance, she summons Virgo who shoots out of the ground to punch Byro in the face. She casts Spica Hole afterwards. When Byro disappears down the hole, Virgo asks for punishment from Lucy. However, the battle is not over as Byro consumes Octopus Liquid that turns his form into that of an octopus and grabs Coco in its tentacles. Virgo tells her that she probably won't be able to do anything about that and Lucy exclaims that she shouldn't give up before she even tries as she dodges one of Byro's tentacles. He crushes the floor next to Lucy and she attempts to climb up a ladder. As she reaches the top, Virgo tosses an extending whip called Fleuve d'étoiles from the Celestial Spirit World to her. As Virgo fades, she states that she thinks it won't be effective but asks her to try using it.
Lucy attempts to strike Byro with her new whip but it is ineffective as she is the one struck down by Byro's tentacle. Lucy then realizes Virgo's concern for her as she provided her with the whip because Lucy's powers have slowly been draining with her consecutive summons. With confidence, Lucy vows that she will not waste Virgo's kindness and extends her whip to catch the tentacle of Byro that's about to crush her. Using this, she manages to spring herself up to Byro's level, runs up his tentacles and orders for him to let go of Coco. She navigates around Byro's body with her whip and exclaims that he should protect Coco because they're allies and that if he doesn't know that much, then she cannot lose. Byro is then shocked as he realizes that his tentacles tangled by Lucy's extending whip.
Suddenly, the Monster Academy that Byro had been leaning on explodes and out comes Natsu who has defeated Hughes and the monsters that he controlled. Byro gets caught up in the explosion and is knocked out as well. Coco, free of Byro's grasp, hands the key to the Dragon Chain Cannon over to Natsu and Lucy, states that she'd rather live happily with her friends than have infinite Magic and pleads for them to destroy the key. However, Sugarboy, strangely floating above the ground, grabs the key before Natsu takes it and flies away. Gray appears on a motorcycle and goes in pursuit after him.
Gray wins in his battle against Sugarboy by tricking him through destroying the original key, attacking him while distracted and then later making a duplicate of the key after Sugarboy lay defeated on the ground. Later, Erza Knightwalker, bleeding and injured, approaches Natsu and Gray after their battles. They are surprised because it is Knightwalker who was victorious in the battle of the Erzas. She knocks both of them out and drags them across the floor. Knightwalker takes them to Faust's room as they have the key to the Dragon Chain Cannon. As she brings them there, she mutters that eternal Magic is upon them.
Knightwalker throws Gray to the floor as she volunteers to Faust the information that Gray can generate the key to the cannon. She orders him to activate the cannon and points her blade to Natsu's neck. Left without a choice, Gray walks over to the cannon. At first, he plans to re-aim the cannon to the Lacrima in order to save their friends. However, he isn't able to do this because he doesn't know how. With Gray in a state of panic and Faust ordering to fire, Knightwalker wakes Natsu and he attacks the Edolas Royal Army. With the guards distracted, Erza takes Faust hostage. She requips back into her original armor and reveals herself to be Erza Scarlet of Earth Land. She orders the soldiers to fire at the Lacrima. While they argue about what to do, Faust yells for them to not worry about him and proceed with firing Extalia. However, the guards do as what Erza told them. The Earth Land Mages' hopes are dashed when Knightwalker, as bloodied and injured as Scarlet, storms in with her spear.
With Faust released, they re-adjust their aim and fire. At this moment, Lucy and Coco arrive on a Legion, shocking Faust. The Earth Land Mages hop on and fly away in an attempt to stop the cannon's fire from hitting its target. Knightwalker looks on angrily. She cuts her hair with her blade and orders the 2nd Magic War Division to pursue them while Faust orders that the Dorma Anim is to be prepared.