The tenth-floor otaku sanctum had never been this loud. Holographic blueprints spun like a tornado of glowing lines, each one annotated in Takumi's snappy programmer shorthand and Veldora's elegant, ancient-dragon calligraphy. Rimuru hovered in the center, trying to look like the responsible ruler while secretly geeking out over the sheer scale of what his big brother had just casually enabled.
Veldora remained firmly planted on his throne of manga volumes, legs crossed in full "wise shut-in philosopher" mode. His black haori now sported a fresh pixel-art patch that read "Support Character MVP." He stroked his chin with one claw, eyes half-lidded in scholarly contemplation. "Probability of catastrophic failure on first prototype: 12.4%. Acceptable margin. Takumi, overlay the transformation sequence from that one mecha anime Rimuru showed me last week. The one where the dragon form does the mid-air barrel roll. Aesthetic is crucial."
"On it, Dragon Bro," Takumi's voice chimed cheerfully inside every head present. "Pulling reference from Rimuru's memory bank. Adding infinite energy flow stabilizers so it doesn't accidentally nuke the testing grounds. Man, back when I was coding, one misplaced semicolon and the whole VR world crashed. Here? I just think 'don't explode' and it doesn't. Reincarnation perks, am I right?"
Rimuru chuckled, the sound echoing like bubbles in a shaken can. "You two are scarily in sync already. It's like I gained a second overpowered older brother who never leaves his room."
Veldora's golden eyes sparkled with mock offense. "Insolent slime! I am not merely 'shut-in.' I am strategically conserving world-altering power for moments of maximum dramatic impact. Besides, the outside world lacks sufficient ramen variety. Here, I commune with the muses of creation." He gestured grandly, and a fresh bowl of steaming noodles materialized beside him, courtesy of the new Otaku Art Creation Techniques. "See? Efficiency."
Shion, who had refused to leave after the talking-onigiri incident, beamed while cradling Oni-giri the First like a prized sword. The sentient rice ball now wore a tiny chef's hat and floated beside her shoulder. "Lord Veldora's wisdom is unmatched! Oni-giri agrees—he just told me the prototype needs more pink accents for proper intimidation factor."
Benimaru, leaning against a shelf of light novels with his arms crossed, sighed the sigh of a man who had seen too many dragon-induced disasters. "Pink. On a dragon-mecha train. I'm writing the incident report already. Title: 'How Infinite Energy Turned Our National Railway into a Magical Girl Transformation Sequence.'"
A new voice burst through the chamber doors like a pink meteor. "Did someone say transformation sequence?! And mecha?! And dragons?! I smelled fun from three countries away!"
Milim Nava, Demon Lord of Destruction and self-proclaimed best friend of Rimuru, skidded to a halt in full battle dress, eyes sparkling with pure chaos energy. Behind her, a slightly frazzled Diablo trailed, adjusting his butler gloves with practiced nonchalance.
"Lady Milim," Diablo intoned smoothly, "I did advise against teleporting directly into Lord Veldora's private sanctum. One does not simply interrupt a True Dragon's… ah… research."
Milim ignored him, zeroing in on the spinning hologram. "Whoa! That's the coolest train I've ever seen! It's got claws! And wings! Rimuru, you better let me test-drive it or I'll sulk for a whole week!"
Veldora's expression shifted from scholarly to genuinely fond in a heartbeat—the wise elder greeting a fellow dragon with just the right mix of respect and mischief. "Ah, little Milim. Your timing is impeccable, as always. Probability of you demanding to pilot: 99.8%. Welcome. Takumi, prepare a co-pilot seat with maximum candy storage."
"Already done. Added a button that dispenses unlimited cotton candy. Figured the Demon Lord of Destruction deserves premium snacks."
Rimuru floated over to pat Milim's head before she could explode with excitement. "Easy there. This is still a prototype. We're using Veldora's new infinite energy supply to power the MagiTrain network. No blowing up the countryside on day one, okay?"
Milim puffed her cheeks. "Boooring! But fine. As long as it goes vroom and does the cool anime glowy thing."
The creation process unfolded in real time. Veldora's palm glowed with pure golden energy—Infinite Pure Destruction & Creation Generator running at full throttle. Threads of power wove together under Takumi's mental guidance: Creative Technology, Science, and Magic Knowledge Repository supplying hybrid schematics that blended Dwarven engineering, elven mana circuits, and straight-up isekai mecha logic. Skill Creation kicked in next, forging a brand-new Ultimate-adjacent ability for the train itself—[Rail-X, Lord of Swift Transit]—then Duplication and Gifting sealed it.
A shimmering portal of light opened in the center of the chamber. Out rolled the prototype: a sleek, obsidian-and-gold carriage the size of a small house, emblazoned with Tempest's crest. It hummed with restrained power. Then, with a dramatic ka-chunk, it transformed. Wings unfurled, claws extended, and the front morphed into a majestic dragon head complete with glowing eyes. A cheerful synthetic voice (courtesy of Takumi's Otaku Art Creation) boomed:
"Tempest Rail-X online! Ready for boarding, otaku overlords! Destination: anywhere cooler than here!"
Shion squealed. "It talks! Oni-giri, take notes—this is how a proper subordinate announces itself!"
Oni-giri bobbed politely. "Understood, Mistress. Shall I practice my own catchphrase? 'Rice and righteousness'?"
Benimaru pinched the bridge of his nose harder. "We're doomed."
Rimuru couldn't stop grinning. The brotherly dynamic felt electric—Veldora supplying raw infinite power and ancient wisdom, Takumi injecting pure programmer-otaku ingenuity, and himself acting as the glue that kept it from becoming a full-blown apocalypse of fun. He probed the new energy link in his core; it felt like a warm, endless river flowing not just to him but to every subordinate in Tempest. No more mana shortages. Ever.
"Alright, small test run," Rimuru declared. "We'll take it up to the surface testing track. Veldora, you coming?"
The dragon lord reclined deeper into his throne, summoning another holographic screen that displayed live feed from the prototype's cameras. "Nay, little brother. I shall observe from my Fortress of Solitude. One must maintain proper distance for objective analysis. Plus, the new volume of Slime Hero Chronicles just dropped in your memory archives. Takumi and I have… critical research to conduct."
"He means we're gonna binge while backseat-driving the test. Multitasking, baby."
Milim was already climbing aboard, dragging Diablo with her. "Shotgun! The butler can be my co-pilot—he looks like he needs more excitement in his life."
Diablo smiled thinly. "As you wish, Lady Milim. Though I do hope the seatbelts are reinforced against… enthusiastic piloting."
The prototype lifted smoothly on anti-gravity fields, phasing through the labyrinth ceilings thanks to a quick Skill Gifting from Veldora. On the surface, in a wide clearing outside the capital, the Rail-X touched down amid a crowd of curious monsters. Gobta and a squad of goblin riders had been "accidentally" summoned by the energy ripple.
"Whoa, Boss! That thing's huge!" Gobta yelped, then tripped over his own feet as a stray thread of infinite energy brushed him. Suddenly, his [Goblin Step] skill duplicated and upgraded on the spot—now he was zooming around at hyper speed, leaving afterimages. "W-wait, I can't stooooop—!"
Benimaru facepalmed for the third time that hour. "Gobta! Control your legs!"
Shion laughed so hard she dropped her tray (Oni-giri caught it mid-air like a pro). "See? Lord Veldora's gifts are blessings! Even the goblins are training now!"
From the holographic feed in the sanctum, Veldora's voice boomed across the field, wise and booming yet laced with otaku glee. "Observe, mortals! The infinite energy generator shares freely. Takumi's design ensures no overload—merely… character development opportunities. Probability of Gobta learning balance through chaos: 100%."
Takumi added helpfully,"Think of it as a free DLC patch for the whole nation. Side quest: 'Don't Trip Over Your New Stats.'"
Milim, at the controls, slammed the "transform" button. The Rail-X roared, shifting into full dragon-mecha mode and doing a perfect low-altitude barrel roll that somehow didn't destroy a single tree. "This is awesome! Rimuru, we gotta mass-produce these yesterday! I'll even help name the limited-edition color variants—'Destruction Pink' is totally a thing!"
Rimuru, floating alongside on a small energy platform, felt the weight of leadership lighten for the first time in weeks. The new skills weren't just power—they were joy. Veldora, the eternal shut-in, had become a fountain of wonders without ever leaving his cave. Takumi's tragic-yet-hilarious death had gifted them all a second chance at creation. And the brotherly bond? Stronger than any Ultimate Skill.
But as the Rail-X completed its flawless test loop and landed amid cheers, a faint anomaly pinged in Ciel's analysis. A tiny rift of creative energy had flickered at the edge of the field—nothing dangerous, but curious. Almost like an accidental window into another possibility.
Veldora's voice turned thoughtful over the link. "Hmph. Interesting. Faust's new investigative depth suggests… visitors may soon arrive. Or perhaps creations from other worlds. Either way, little brother, our supply line stands ready. Infinite energy, infinite stories."
"And infinite merch," Takumi quipped. "I've already sketched the model kits."
Rimuru sighed happily, watching his people celebrate. "You two are going to be the death of my paperwork… and the life of this nation."
Milim hopped off the Rail-X and tackled him in a hug that nearly popped his slime form. "Group adventure when the real trains are done? Promise!"
"Promise," Rimuru laughed. "Just… no destroying continents for fun."
In the depths, Veldora leaned back, bowl of ramen in hand, a small proud smile on his face. "Well played, Takumi. The shut-in dragon has supplied his family. Now, back to research. Next episode awaits."
The winds over Tempest carried the hum of new beginnings—plus the distant sound of Gobta still zooming uncontrollably in circles, yelling something that sounded suspiciously like an anime battle cry.