The testing field still smelled faintly of scorched grass and overexcited goblin aftershave. The Rail-X prototype sat innocently in carriage mode, its dragon-head front module humming a cheerful idle tune that Takumi had programmed to sound like the opening theme of a certain isekai about overpowered butlers. Gobta had finally been pried off his hyper-speed loop by three orcs and a very patient dryad, while Pixeldora the pixel-dragon mascot perched on his shoulder like a living fidget spinner, chattering about "beta patch notes."
Rimuru floated above the crowd, arms crossed in his tiny slime form, trying to project "responsible ruler" energy while internally screaming at Ciel to log the repair costs. "Alright, test officially over. No more yeeting. No more accidental summons. We're moving to phase two tomorrow—actual track laying with the dwarves. Everyone, go home and pretend this was a controlled demonstration."
Milim, still vibrating from pilot-seat adrenaline, pouted dramatically. "Booo! But Diablo didn't even get a turn! He's been sulking in the co-pilot seat like a fancy statue the whole time. Come on, Rimuru! Let the pretty butler drive! Pretty please with destruction on top?"
Diablo adjusted his pristine white gloves with deliberate slowness, his crimson eyes half-lidded in that signature mix of polite menace and butler perfection. A faint smile played on his lips—the kind that suggested he had already calculated seventeen ways to turn this into an elegant disaster for anyone who annoyed his mistress. "Lady Milim flatters me. However, I am merely a humble servant. Piloting experimental draconic mecha falls outside standard tea-serving protocols. Unless, of course, Lord Rimuru deems it… necessary."
From the depths of the tenth-floor sanctum, Veldora's voice rolled across the mental link like a wise professor who had just discovered a new flavor of instant ramen. "Hmph. Necessary? Probability that our resident demon butler secretly desires to pilot a giant robot: 97.2%. Takumi, prepare the custom interface. It is time for the shut-in dragon to bestow a gift worthy of such refined chaos."
Takumi's voice chimed in, equal parts programmer nerd and otaku hype-man. "Already on it, Dragon Bro. Pulling from the Creative Technology Repository—mixing your infinite energy generator with some old-school mecha anime tropes I loved coding back in my salary-slave days. Remember that seventy-two-hour crunch where I died mid-hype? Yeah, this is basically my redemption arc. Diablo's getting a personalized skill set. Name pending—something cool like 'Elegant Annihilation Mode.'"
Rimuru blinked, sensing the golden thread of pure creation energy snaking upward from the labyrinth. "Wait, you're just going to—Veldora, you can't keep handing out custom Ultimate-adjacent skills like party favors! Last time you did that, Gobta became a temporary Gundam."
Veldora's chuckle was deep, scholarly, and utterly unrepentant. "Nonsense, little brother. As the elder supplying infinite destruction and creation to all Tempest subordinates, I merely optimize. Faust's new sub-skills demand testing. Skill Creation for allies? Check. Skill Duplication and Gifting? Double check. Besides, Takumi insists this will produce 'peak cinema.' I concur. Observe."
A soft ping echoed in Diablo's core. The demon's posture didn't change—still the picture of butler elegance—but his eyes sharpened with predatory delight as data flooded his mind.
New Skill Acquired: [Diablo Protocol – Lord of Refined Annihilation]Sub-skills granted via Veldora's Infinite Supply:
Otaku-Enhanced Mecha Piloting (perfect synchronization with any vehicle, plus dramatic pose bonuses) Infinite Energy Resonance (draws directly from Veldora's generator for zero-cost ultimate techniques) Creative Destruction Styling (transforms attacks into aesthetically pleasing, butler-approved flourishes) Skill Storage & Duplication Buffer (can archive and gift minor skills mid-battle for "polite" support)
Diablo's smile widened by a single, terrifying millimeter. "My, my. Lord Veldora and his… enthusiastic co-pilot are most generous. I feel positively invigorated. Shall we demonstrate, Lady Milim?"
Milim's eyes sparkled like stars about to supernova. "YES! Shotgun co-pilot again! But this time you drive and I backseat-destroy things!"
Shion clapped her hands so hard the sound cracked nearby crates. "Lord Diablo in a mecha?! Oni-giri, record this! It shall inspire new recipes—'Butler's Elegant Annihilation Ramen'!"
Oni-giri bobbed solemnly, voice dripping with dry wit. "As you wish, Mistress. Though I suspect the ingredients will mostly be 'regret' and 'explosive flair.'"
Benimaru, who had finally stopped aging visibly from stress, pinched the bridge of his nose. "I'm going to need a vacation. In another dimension. Preferably one without dragons or demons with new toys."
The Rail-X's cockpit hatch hissed open invitingly. Diablo stepped forward with the grace of a shadow gliding across silk, then paused at the threshold. He turned to the crowd, one gloved hand on his chest in a perfect bow. "Fear not, citizens of Tempest. I shall pilot with the utmost decorum. No unnecessary property damage. Unless Lady Milim requests it, in which case… I shall ensure it is artistically executed."
Takumi laughed in everyone's heads. "Dude's already role-playing the final boss butler. I love it. Dragon Bro, queue the transformation BGM from that one series where the calm guy goes full psycho in the cockpit."
Veldora's response was pure scholarly mischief. "Done. Volume at 120%. Begin the demonstration."
Diablo slid into the pilot seat like he was born for it. The controls lit up in elegant crimson and gold, reshaping themselves to fit his grip perfectly—courtesy of Otaku Art Creation Techniques. The Rail-X's synthetic voice (now upgraded with a suave British filter Takumi had clearly stolen from Rimuru's memories) announced: "Diablo Protocol online. Elegant Annihilation Mode engaged. Please fasten your seatbelts and prepare for refined devastation."
Milim bounced in the co-pilot chair, already munching on the unlimited cotton-candy dispenser. "Go go go! Make it do the spinny thing but classy!"
The prototype rose smoothly—no reckless roar, just a low, refined hum like a perfectly tuned orchestra warming up. Then it transformed. Wings unfolded with mechanical precision, claws extending in a slow, deliberate arc that somehow looked like a formal bow. The dragon-head module's eyes glowed a deep, aristocratic red.
Diablo's hands moved across the controls with butler-level efficiency. "Initiating test maneuver alpha: Shadow Waltz." The Rail-X executed a flawless mid-air spin, energy trails forming intricate patterns that spelled out "Tempest" in flowing calligraphy. A stray thread of infinite energy brushed a nearby boulder; instead of exploding, it politely reshaped into a perfect miniature statue of Rimuru giving a thumbs-up.
The crowd gasped. Then cheered.
From the sanctum link, Veldora's voice boomed with wise approval. "Magnificent control! Probability of Diablo achieving zero collateral damage while still looking fabulous: 100%. Takumi, note this for future skill gifting—elegance multiplier applied."
"Copy that. Adding 'Butler Aesthetic' as a hidden stat. Rimuru, your demon just turned our mecha into a luxury sports car with teeth. Sales are gonna skyrocket."
Rimuru hovered closer, half impressed, half terrified of the paperwork. "Diablo… you're enjoying this way too much, aren't you?"
The demon's voice came back smooth as aged wine over the comms. "Merely fulfilling my duties, my lord. A proper servant must master every tool at his disposal. Even one that transforms into a dragon and dispenses snacks." He flicked a switch. The Rail-X's claws extended into elegant energy blades, slicing through a practice target with surgical grace—leaving behind a trail of sparkling cherry-blossom petals because of course Takumi had added that.
Milim whooped. "Do the destruction beam next! The pretty one with the sparkles!"
Diablo inclined his head as if she had asked for more tea. "As you wish." A focused beam lanced out—not wild like Milim's usual style, but a precise, glowing lance that carved a perfect circle in the sky before fizzling into harmless fireworks. The synthetic voice purred: "Target neutralized with style. Would you like a complimentary macaron?"
Benimaru finally cracked a reluctant grin. "Alright, I admit it. That was… annoyingly perfect."
Shion squealed, hugging Oni-giri so tight the rice ball squeaked. "Lord Diablo is a genius! Oni-giri, we must learn this elegance for our next cooking battle!"
Oni-giri sighed in tiny resignation. "Mistress, I believe the mecha already has enough ego. Shall I prepare a victory onigiri instead?"
The demonstration ended with the Rail-X landing in a perfect three-point pose, wings folding like a gentleman adjusting his coat. Diablo emerged first, offering Milim a hand down as if escorting her from a carriage rather than a giant robot. She took it, still bouncing. "That was the best! You were all calm and then BAM—fancy lasers! We're doing this every week, right?"
Diablo's smile never wavered. "Only if Lord Rimuru approves. And only if the tea service schedule remains uninterrupted."
Rimuru landed between them, feeling the brotherly warmth from Veldora's link stronger than ever—the infinite energy now threading not just through the nation but through moments like this, turning potential disasters into shared laughter. "You did great, Diablo. Scary great. Veldora, Takumi—thanks for the upgrade. But next time, maybe warn me before you turn my strongest subordinate into a mecha pilot?"
Veldora's reply was warm, wise, and laced with shut-in satisfaction. "Where is the fun in warnings, little brother? The world is our canvas now. Takumi and I shall remain here, refining further gifts from the Fortress of Solitude. After all, one must balance supply with… critical binge research."
"Translation: we're watching the mecha episode I just created using Otaku Art Techniques. You're all welcome to the director's cut later. Spoiler: Diablo gets a cape."
Diablo bowed deeply to the empty air. "I would be honored. Though I insist on black silk. Red accents clash with my aesthetic."
As the crowd dispersed—Gobta begging for "just one more speed boost," Pixeldora already sketching mascot merch—Rimuru felt the unique dynamic click deeper. Veldora the wise, funny otaku dragon supplying endless possibility from his manga cave. Takumi the reincarnated programmer adding that chaotic creative spark. And now Diablo, the perfect butler, seamlessly integrating into the mecha madness with style that somehow made the whole thing feel… inevitable.
The MagiTrain project had just gained its most elegant test pilot. And Tempest? It was about to get a whole lot more entertaining.