Three days later, in the Grand Plaza of Magnolia Town.
Natsu and Erza stood opposite each other, surrounded by a dense crowd of townspeople and the mages of Fairy Tail. Goku was right there in the front row.
Today was the day of Natsu's promised duel with Erza. Goku wouldn't miss it for the world—partly because of the agreement that the winner would fight him next, and partly because he was genuinely fascinated by this style of combat.
It felt nostalgic, like standing in the wings of the World Martial Arts Tournament watching other competitors' matches. By observing the strong, he could find gaps in his own style and continue to evolve.
"Go for it, Natsu!"
"Titania! Give that brat a lesson he won't forget!"
Amidst the cheers of the townspeople, the battle officially commenced.
"Requip: Flame Empress Armor!"
A crimson magic circle flared beneath Erza's feet. In a flash of light, she was clad in a stunning set of red-and-orange armor that radiated an intense heat.
"The Flame Empress Armor... it has high fire-resistance properties. Natsu's in trouble now," the spectating mages noted. They were well-acquainted with Erza's tactical versatility.
"With that armor, Natsu's fire damage will be cut by at least half."
"Looks like Erza is taking this seriously from the start."
"Begin!" Master Makarov announced through a magical megaphone. As Master, he encouraged healthy competition; it was the fastest way for his mages to grow. Today, he acted as the official referee for both matches.
"Flame Empress Armor, huh? Fine! Now I don't have to hold anything back!" Natsu wasn't intimidated; he was ecstatic. He wreathed his limbs in flames to boost his speed and explosive power, launching himself at Erza like a living comet.
Erza met him head-on, her Flame Empress Sword clashing against Natsu's fiery fists in a flurry of sparks and shockwaves.
"Whoa, they're really good!" Goku's eyes sparkled.
To be honest, he much preferred the mages here to the wizards back at Hogwarts. These mages fought in a way that felt familiar to him. While they used elemental spells, they didn't just stand back and wave sticks; they preferred to coat their bodies in magic for brutal, close-quarters combat.
Natsu used his fire as an extension of his martial arts, only unleashing massive range attacks when the timing was perfect. Goku fought the same way—he rarely opened with a Kamehameha.
Instead, he used ki to reinforce his physical body for high-speed brawling. While energy blasts were powerful, they consumed more energy and were easier to dodge. Against a true expert, a fist reinforced by ki was often far more reliable than a beam.
Erza's Requip magic functioned on the same logic. While her armors gave her elemental edges, her true strength lay in her decades of combat experience, her refined techniques, and her physically transcendent body.
In this world, the strongest mages weren't just "casters"—they were elite martial artists who had seamlessly integrated magic into their combat forms.
"Erza! Take this! My ultimate move!"
After ten minutes of high-intensity clashing, Natsu realized he was still being outclassed in both technique and raw magic capacity. He leaped high into the air, distancing himself for a finisher.
"The fire in my right hand... and the fire in my left... combined! Fire Dragon's Brilliant Flame!!"
He slammed his hands together, merging two distinct types of flames into a massive, swirling sphere of gold and red fire. The heat was so intense it began to singe the hair of the people in the front row.
"Is he trying to level the whole town?!" the mages cried out, sensing the sheer volume of magic packed into that sphere. If it hit the ground, Magnolia would be replaced by a crater.
"Relax, relax," Makarov said calmly. He wasn't worried. With Erza there, that fireball would never touch the town. Natsu knew that too, which was why he felt safe going all-out.
Makarov noted that the raw power of this move had officially reached the baseline of an "S-Class Mage"—at least by the standards of ordinary guilds. Of course, Fairy Tail's S-Class requirements were much higher, bordering on Wizard Saint levels. He glanced at Goku and smiled. After the Eisenwald mission, he was certain Goku was already at that elite level; he just needed a formal exam to make it official.
Goku, meanwhile, was staring at the Brilliant Flame with deep concentration. He noticed that the fire in Natsu's hands wasn't fundamentally different, but by swirling them together in a specific way, the destructive output increased exponentially.
'I can use that,' Goku thought. 'If I take the ki from my left hand and the ki from my right and spin them together into a ball... it should be way more explosive than a standard ki blast.'
"Flame Empress Slash!"
Faced with the miniature sun descending upon her, Erza didn't dodge. She lunged upward, her sword erupting in a pillar of concentrated fire. With a single, vertical stroke, she sliced Natsu's ultimate move clean in half, letting the energy dissipate harmlessly into the sky.
"I need to add more control to it," Goku murmured to himself, watching the fireball break. He realized that if he created his own "Spirit Ball," simply throwing it would be too predictable. He needed to be able to guide it, making it dodge obstacles and track the enemy.