The train clattered steadily along the tracks. Beneath the rhythmic, metallic clicking of the wheels, Erza's strict voice laid out exactly what she had learned during her mission.
Her posture was rigid, her eyes sharp, and her tone clipped. The atmosphere inside the small cabin had shifted to a serious, tense edge—if you ignored the occasional ZAP that jolted through Natsu every few seconds.
Gray looked at Erza, his brows furrowing in confusion. "Lullaby? Isn't that just the name of a sleeping song? Am I missing something here?"
Lucy hummed, tapping her chin as she tried to recall her reading. "Lullaby, lullaby... wait. Where have I heard that before? Wait..." Her eyes went wide, and her expression twisted into one of pure terror. "Isn't that the name of a cursed object?! A death song that kills anyone who hears it?!"
Erza nodded solemnly. "During my return trip, I stopped at a tavern where I overheard a group of rogue mages discussing a cursed artifact. At first, I ignored it. But then I heard the name Erigor. He's a dark mage from the Eisenwald guild who strictly takes assassination jobs. It's why the underworld calls him Erigor the Shinigami. It seems they've located the flute known as Lullaby."
Erza crossed her arms, ignoring the growing dread on her teammates' faces. "And as you correctly guessed, Lucy, Lullaby is a cursed artifact created by the Black Wizard, Zeref. If activated, the spell will—"
ZAP.
Natsu jerked stiffly in his seat like a puppet on strings, his face going completely blank for a second before he snapped back to life. "So we just need to beat up some Shinigami bum? Leave it to me!"
Another ZAP hit him, and Natsu immediately slumped over the armrest again. By this point, no one in the cabin even reacted to it.
Clutching Plue—the small, shivering snowman spirit—to her chest, Lucy looked like she was about to faint. "What did I get myself into? And wait... what exactly is a dark mage? Or a dark guild?"
Erza turned to Lucy, genuinely surprised. "You don't know what a dark guild is?"
Lucy looked down, her cheeks flushing red with embarrassment.
Erza sighed, softening her voice slightly to explain. "They are mages and organizations that operate completely outside the law. They take illegal jobs, commit horrific crimes, and are treated as wanted criminals throughout the Kingdom of Fiore. They are so dangerous that the Magic Council and the Local Guild Masters League have a standing order: take them down on sight."
Lucy immediately pulled out a small notepad, scribbling furiously with trembling fingers. "S-So it's really that dangerous... I should have stayed at the guild." She nervously clutched Happy, who was staring down at the floorboards.
"Lucy," Happy muttered, pointing a paw downward. "Your juice is leaking."
Lucy shrieked, delivering a swift punch to the blue cat's head. "It's not mine! It's water melting off of Plue! Don't make stupid jokes when I'm already terrified out of my mind!"
"It is extremely dangerous, Lucy," Erza assured her, leaning forward with a firm look. "But do not worry. I will personally ensure that nothing happens to any of you."
Kai, meanwhile, remained completely detached from the panic. He sat slouched against the corner of the booth, his arms folded behind his head. His golden eyes were half-lidded and his head was tilted, making it look like he was listening to Erza and ignoring her at the exact same time.
In truth, his mind had completely wandered the second Erza mentioned Lullaby. His expression had shifted into that of a mad scientist who had just stumbled upon a rare, undocumented element. Every so often, the group could hear him muttering under his breath:
"A living cursed artifact capable of killing through sound waves... centuries old with an undocumented material composition and an autonomous magic core... Think of the potential for life-infusion crafting. So many new materials to harvest..."
The rest of the cabin collectively sweat-dropped, giving him a wary look before returning to their own planning.
But as Kai's mind spiraled deeper into thoughts of dismantling the legendary flute, a faint tug pulled at his awareness—like a vibration rippling through a spider's web. His golden eyes sharpened, and he finally looked up.
"—and according to what I overheard, Eisenwald intends to—"
Kai stood up.
Not abruptly, and not with a start. He moved smoothly, effortlessly, as if he had always intended to stand up at this exact second and the time was simply right.
Before Lucy could even blink, Kai was already standing by the sliding door leading to the next train car.
"Kai?" Lucy whispered, confused.
He didn't answer.
Instead, his fist shot out sideways—straight through the reinforced wooden partition wall of the train.
Wood splintered violently. Metal bent with a screech. A sharp, terrified scream erupted from the other side of the wall—
And then, the next cabin exploded.
The entire train lurched violently to the left. A powerful shockwave rattled the glass windows, sending Lucy crashing hard into the opposite seat.
"What the—?!" Gray yelled, instantly jumping to his feet.
"WHAT HAPPENED?!" a panicked passenger shouted from two cars back.
Erza stood up instantly, a steel sword materialized into her hand in a brilliant flash of red storage magic. "Kai! What did you do?!"
Kai calmly pulled his fist back through the shattered hole, casually dusting a few splinters off his knuckles.
"I felt someone standing right there," he said evenly, acting as if he hadn't just punched a hole through a moving train. "I was ignoring it for a few minutes. But he stayed there too long to be a bystander or a conductor. So, I focused." He tapped his temple with two fingers. "Dark magic. Thick, familiar, and stupidly close to us."
Lucy's blood ran cold. "You mean—"
"That was likely an Eisenwald scout," Kai finished. "And judging by how fast he scrambled, he might even be the one carrying Lullaby."
The entire cabin froze. The reality that they had been sitting mere feet away from a death-dealing artifact made the air turn icy.
Natsu twitched again, forcing himself up by sheer will and shaking his fist. "Let's go! We gotta catch him! I've always wanted to fight someone on top of a train! I want to know what it feels like to fight without motion sickness!"
ZAP.
Another shock surged through him, and Natsu froze mid-shout.
Gray sighed, looking down at his rival with pity. "If you fight like that, freezing up every two seconds, the bad guy is just gonna laugh at you, flame-brain."
"What did you say, ice fairy?!" Natsu snapped, throwing himself at Gray's collar. "I can beat you and that dark mage with my eyes closed!"
Erza's jaw clenched. "Shut up, both of you! We need to pursue him!" She stepped toward the gaping hole in the wall, preparing to leap out into the rushing wind—
But Kai's arm extended, blocking her path.
"No."
Erza stared at him, her eyes narrowing. "What are you doing? Move."
"No."
"Kai—"
"Think for a second, Red." His tone softened, but it carried a sharp, unyielding logic. "If you managed to overhear their plan in a random tavern, they aren't stupid. They'll expect someone to follow them. That runner is almost certainly a decoy to draw us away."
His eyes flicked back toward the resting Natsu and Gray.
"If all of us jump off this train right now, the upcoming station will be completely defenseless. Eisenwald could ambush it without firing a single shot."
Even Erza hesitated, her sword lowering slightly.
Kai tilted his head, a faint smirk playing on his lips. "You handle the station. I'll chase the runner." He turned back toward the shattered gash in the train wall.
"Wait." Erza grabbed his wrist.
Kai stopped, looking back over his shoulder.
"If that person truly has Lullaby..." Erza's grip tightened, her sharp eyes boring into his. "...you may be in severe danger."
The amusement in Kai's golden eyes expanded. "Red, are you actually worried about my safety? Or are you just terrified that I'm going to take that artifact and upgrade my workshop?"
Erza's grip tightened even further. She didn't confirm it... but she didn't deny it either.
Lucy stared between the two of them, a cold sweat breaking out on her neck. Their dynamic was incredibly complicated.
"Lucy. Happy," Erza said suddenly, snapping her head toward the blonde celestial mage and the blue Exceed.
Both of them blinked in unison. "Huh?"
"Go with Kai."
"WHAT?!" they both screamed.
Erza crouched down, lowering her voice so only Lucy could hear over the roaring wind. "I cannot leave this train. I need to secure Oshibana Station, and I have to keep an eye on Natsu and Gray. I absolutely cannot send those two idiots with Kai."
"HEY!" the idiots in question barked from the background.
Erza ignored them entirely. "Kai is... efficient. If he goes alone, he won't hesitate to beat the scouts into critical condition, tie them to the tracks, or hand them an explosive to see what happens. He needs a conscience with him."
"You say that like he's actually done that before..." Lucy whispered, horrified.
Erza looked away, deliberately avoiding her eyes. Lucy paled drastically.
"Kai won't do anything reckless to you," Erza continued, trying to reassure her. "You're a new member. You aren't... close enough to him yet. He won't risk hurting a bystander."
Lucy blinked. "But... didn't he brutally beat you in a duel? And you're a girl!"
Erza sighed heavily. "That is because we have been friends for years. He knows my limits. He doesn't know yours. Now go."
"W-What kind of terrifying logic is THAT—"
"Just go!"
Lucy gulped, nodding stiffly in absolute defeat. Happy saluted beside her, his paws trembling. "A-Aye..."
Lucy then looked out the shattered wall, a sudden realization hitting her. "But wait! The guy jumped off the train minutes ago! The train is still moving at full speed! By the time we find a way off—"
"We'll never catch him!" Happy finished miserably.
Kai finally turned around, looking thoroughly entertained by their panic. "You two done writing your wills? Good. Let's move."
Before Happy could protest, Kai scooped the cat up by the back of his green vest.
"Wahh! Put me down!"
"Get on, blondie," Kai commanded, gesturing to his back.
Lucy's face flushed, but given the alternative of being left behind with an angry Erza and a motion-sick Natsu, she jumped onto his back, locking her arms around his neck. "W-Wait! How are we supposed to safely exit a moving train—?!"
Kai grabbed the metal ceiling rod of the cabin with one hand. "Who said anything about safely?"
And then, he flipped.
Backward. Straight through the jagged hole in the wall.
Lucy screamed at the top of her lungs. Happy screamed even louder.
They hung upside down in the open air for a single, horrifying second—Lucy clinging to Kai's shoulders for dear life, Happy flapping his wings wildly—before Kai twisted his body mid-air, defying momentum, and landed perfectly on the rushing roof of the train.
Lucy and Happy collapsed limply against his coat.
"We're... we're alive?" Lucy whimpered into his shoulder.
Kai didn't bother answering. He was already sprinting along the moving roof. The harsh wind tore through his slicked-back hair and caused his long coat to flare out like wings, but his footing remained impossibly steady.
"K-Kai! SLOW DOWN!" Lucy cried out, the wind eating her words.
"Why? Where's the fun in that?"
"FUN?!"
As he ran, Kai reached into his side pouch with his free hand. Lucy stared in absolute disbelief as his fingers began blurring, pulling out gears and metallic parts.
"YOU'RE TINKERING WHILE RUNNING?!"
Kai hummed contentedly. "It's called efficiency, blondie."
Metal springs, brass runes, pieces of enchanted scrap metal, and tiny lacrima crystals danced between his fingers in a fluid, impossible rhythm.
Up ahead, the edge of the train car approached. Kai leapt into the open air. Lucy squeezed his neck tight, shutting her eyes, while Happy grabbed onto Kai's hair.
Mid-air, Kai slapped his newly assembled gadgets onto the soles of his boots. A bright burst of blue light erupted as a golden magic circle flashed beneath his feet. With a series of mechanical clicks and whirs, the metal morphed.
Literal, high-speed inline wheels sprouted from the soles of his shoes.
"Oh no," Lucy whispered.
"Oh yes," Kai corrected cheerfully.
They hit the ground just past the tracks. The wheels struck the dirt path with a sharp screech—and then they shot forward like a literal bullet.
Lucy: "AAAAAAAAAAAAAAAAAAA—!"
Happy: "WE'RE GONNA DIE!!!"
Kai: "Quit complaining. I even provided safety handles."
Lucy glanced down at his shoulder through her tear-blurred eyes. Attached to his coat was a detailed, multi-legged metallic spider.
"WHAT HANDLES?! THAT'S A METAL SPIDER!"
"That's Pixie, my workshop assistant," Kai replied smoothly. "Hold onto her legs if you don't want to achieve escape velocity. Because we're about to take off."
The path ended in a steep drop-off into a valley. Lucy and Happy squeezed their eyes shut, each grabbing one of Pixie's cold, metallic legs. The mechanical spider immediately reacted, extending its remaining legs to tightly lock Lucy and Happy firmly against Kai's back.
"We're gonna crash, we're gonna crash! I need to summon Aquar—" Lucy yelled, reaching for her keys.
Kai smirked, his fingers snapping. "Feather Fall."
A soft, weightless white glow shimmered beneath them, casting a magic circle identical to the one Lucy had seen during his fight with Erza. Suddenly, their violent plunge turned into a graceful drift. It felt as though gravity had been completely replaced by a bed of cotton.
Lucy cracked one eye open. "Oh... we're floating." She quickly let go of her gate keys, letting out a sigh of relief. If she had summoned Aquarius into a dry valley, the spirit probably would have drowned her—or worse, Kai might have stolen the key again.
The moment they touched the valley floor, Kai hit the ground running. His customized roller-skates screeched against the dirt as he carved through the rough terrain, flawlessly maintaining a ridiculous speed as he closed the distance on the fleeing dark mage.
Lucy finally dared to look up. Ahead of them, a figure in a white cloak was sprinting desperately through the thick underbrush.
"THAT'S HIM!" Happy pointed dynamically.
Kai grinned, accelerating effortlessly. Lucy tightened her grip on his shoulders, shouting over the wind, "Kai... are these skates actually safe, or are they going to explode like your other inventions?!"
"Yeah, maybe?"
"You're completely insane!"
"Probably."
Happy sighed miserably from her side. "We know."
Kai's grin only widened. "But you're not dead yet. So, you're welcome."
Back on the train, Gray and Natsu stood by the shattered wall, watching the distant cloud of dust kick up from Kai's skates until the trio shrank into tiny specks.
Natsu sagged against the frame, his stomach turning again as he twitched. "I... I still want to go fight..."
Gray exhaled, shaking his head. "I honestly don't know whether to admire your stupidity or beat you up for wanting to fight in that condition."
Erza stood silently behind them, her arms crossed tightly over her chest armor. Her sharp eyes remained fixed on the horizon where Kai's silhouette had disappeared.
"He'll handle it," she muttered quietly.
Gray blinked, turning to her. "Huh? You actually trust him with this?"
Erza didn't answer immediately. Her fingers subtly brushed against the armor protecting her lower back—the exact spot where she could still feel the lingering ache of his kick from yesterday. The spot where he had leaned in, whispered so softly, and then launched her into a wall.
She let out a long, controlled exhale. "Annoying as he is... yes. I trust his strength."
Gray and Natsu exchanged a wary look.
"But," Erza added under her breath, her right eye twitching violently, "if he dares to touch that flute or use it for one of his twisted experiments when he gets back... I will personally dismantle him."
Gray looked at her, sweating. "Uh, Erza? You will what?"
Erza snapped out of it, sighing as she turned away from the hole. "Nothing. Let's focus on our own task. We are already approaching Oshibana Station. We need to intercept Erigor and his main force quickly, so we can secure the area and regroup with Kai and Lucy before he does something irreversible with that artifact."
Meanwhile, in the grand conference hall of Clover Town, Master Makarov was chatting animatedly with the other masters of the Legal Guild League. The masters of Blue Pegasus, Lamia Scale, Quatro Cerberus, and various others were gathered around, enjoying drinks before the official meeting began.
Bob, the flamboyant Guild Master of Blue Pegasus, laughed in his usual sing-song voice, spinning around dramatically. "Macky~! Your wizards are always so full of youth and life! I even heard a lovely new girl joined your ranks recently."
Makarov chuckled proudly, taking a sip of his beer. "Ah, you mean Lucy? Yes, she just joined up! And let me tell you, Bob, she is incredibly talented, supple, and voluptuous!"
Bob covered his face with his hands, giggling. "Oh, so naughty~!"
Goldmine, the stern Guild Master of Quatro Cerberus, turned to Makarov with an annoyed grunt. "Your wizards may be free-spirited, Makarov, but they are entirely too destructive. The Magic Council is constantly complaining that one of these days, Fairy Tail is going to accidentally erase an entire city from the map. You need to keep them on a shorter leash."
Makarov just laughed it off, taking another deep gulp of his drink. He muttered jokingly, "Hey, if I'm going to be destroyed, I wouldn't mind it being by Lucy's—"
"Macky, you shouldn't talk about your subordinates like that," Bob chided with a chuckle.
Just then, a magical messenger bird fluttered through the high windows of the hall. It hovered over the tables, calling out to get their attention. "Master Makarov! Master Makarov! A letter from Mirajane! A letter from Mirajane!"
Makarov blinked, turning toward the bird. He took the sealed letter and tapped the magical emblem on the front. The seal dissolved into a glowing magic circle, and a small, vibrant projection of Mirajane appeared in the air.
"Master! I'm so glad you reached the conference building without any trouble," the hologram of Mira said with her signature sweet smile.
Makarov hummed happily, waving his hand to draw the attention of the other masters. "Hey, look everyone! It's Mira! Our guild's poster girl. Isn't she just the cutest?"
The other masters turned, nodding in approval. "Ah, she really is beautiful. She's grown into a very mature young lady."
The projection of Mira laughed sheepishly, rubbing the back of her head. "Actually, Master, I wanted to give you a quick update. Erza and Kai returned to the guild yesterday, and this morning, they unexpectedly took a mission together! Right now, Erza, Kai, Natsu, Gray, and Lucy are all working as a single team. This might honestly be the strongest team Fairy Tail has ever put together!"
While Mira smiled brightly, completely innocent and happy, Master Makarov's entire soul literally departed from his mouth. His body turned a stark, chalky white as he trembled violently, his drink slipping from his numb fingers.
"Erza... and Kai... and Natsu... and Gray..." Makarov muttered, his voice cracking in pure, unadulterated terror. "All in the same place... working together... WHY?!"
The surrounding Guild Masters looked at the crumpled, shivering Makarov with deep, profound pity.
"Poor guy," Goldmine muttered, sighing. "Looks like the Council's prediction about a city getting leveled might actually come true this week. But wait... who is this 'Kai' kid? I feel like I've been hearing that name a lot lately..."