The grimoire hung in the air, a silent sentinel before Genos's sputtering core.
On its first open page, an image resolved itself from the yellowed parchment. It wasn't a spell chant. It wasn't a summoning circle.
It was a schematic.
A flawless, impossibly detailed blueprint shimmered on the page. Lines of golden light crisscrossed with silver arcs, depicting a device that was part-engine, part-organ. Intricate notes were scrawled in the margins, in a language that was neither from this world nor Genos's. Yet, he understood it. The logic was pure engineering.
"It is…" Genos breathed, his voice laced with synthetic static and sheer awe. "A magi-catalytic energy converter. With a runic coolant cycle."
He recognized the principles. The design mirrored theoretical next-generation power systems Dr. Kuseno had only hypothesized. But this blueprint was infused with something else—the fundamental laws of magic. It proposed using ambient mana not as a contaminant, but as a primary fuel and coolant simultaneously.
It was perfect. It was impossible.
"Can you build it?" Saitama asked, walking over to peer at the page. "Looks complicated."
"The design is flawless," Genos said, his mind racing. "But I lack the necessary components. I need a mana-conductive filament to serve as the primary catalyst. And a method to… 'weave' the initial runic matrix into my existing power lines without a full system shutdown."
He was thinking out loud, running a diagnostic of his own dwindling capabilities. The project was too delicate. The risk of total core meltdown was 97.4%.
"Weaving, huh?"
Vanessa stood up, her wine bottle set aside. She sauntered over, her movements lazy but her eyes sharp. "I might know a thing or two about that."
She looked at Genos, then at the blueprint. Her fate-altering magic, which saw the red threads of causality, could see a new, shimmering golden thread materializing from the grimoire and trying to connect to Genos. It was unstable, flickering.
"My thread magic can manipulate fate," she said. "I guess it could probably handle a few magical wires, too. I can be your filament."
Yami snorted from his chair. "Show-off."
"Okay," Genos calculated. "With a live magical conduit, I can manually guide the integration. But the energy feedback will be extreme. One stray arc could incinerate you."
"I'll take my chances," Vanessa said with a wink. "Beats listening to Magna's yelling."
Asta stepped forward, holding up his Demon-Slayer Sword. "What about me? What can I do? My Anti-Magic—it could stop any stray magic, right? I can act as a shield! A grounder!"
Genos looked from the earnest boy to his fading core. Asta's ability was a wild card, but the logic was sound. An Anti-Magic field could potentially isolate the operation, preventing runaway magical reactions.
"Affirmative," Genos said, a new tactical plan forming. "Asta, you will stand by to negate any uncontrolled mana discharge. Vanessa, I will expose my primary core manifold. You must use your thread magic to create a direct bridge from the ambient atmosphere to the intake nodes."
He didn't have a workbench, so he knelt on the floor of the common room. With a hiss of hydraulics, the armored plating on his chest peeled back, revealing a terrifyingly complex array of wires, conduits, and the flickering red heart of his machine body.
The Black Bulls gathered around, their usual chaos replaced by a tense, focused silence.
"Beginning procedure now," Genos announced.
Vanessa's grimoire opened. "Rogue's Thread," she murmured. A single, shimmering red thread emerged from the page, finer than silk. She guided it with practiced grace toward Genos's exposed core.
"Now!" Genos commanded.
The thread touched the intake node. For a moment, nothing happened. Then, the room's mana—the very air they breathed—was sucked toward the thread, funneling into Genos's core in a violent, uncontrolled torrent.
The core flared from red to a blinding white. Alarms shrieked from Genos's internal systems. "Overload! Core temperature rising past critical limits!"
"I can't hold it!" Vanessa grunted, sweat beading on her brow. The thread was vibrating wildly, threatening to snap.
"Asta!"
Asta was already moving. He slammed the flat of his blade onto the floor beside Genos, not touching him directly. "Not yet!"
A wave of Anti-Magic washed outward, a null-space that didn't destroy the mana but corralled it, calming the violent flood into a steady, manageable stream flowing down Vanessa's thread.
Genos's optics glowed with intense focus. "Flow stabilized. Re-routing power. Integrating runic cycle." His fingers, now detached from his arm and crawling like spiders over his own chest, rewired conduits with inhuman speed, following the blueprint still glowing on the floating grimoire's page.
Blue light began to trace glowing, runic patterns across his core housing. The shrieking alarms subsided, replaced by a deep, resonant hum.
The angry red light in his chest softened, cooled, and settled into a steady, brilliant blue.
The procedure was complete.
With another hiss, the chest plates slid back into place. Over the newly sealed core, the golden rune that had first appeared on the grimoire's cover blazed for a second before fading into the metal.
Genos stood up. He felt… powerful. More than ever before.
"System diagnostics complete," he announced, his voice crisp and clear. "All functions nominal. Energy core operating at 135% of previous peak capacity. Ambient mana is successfully being converted into stable energy."
He turned to the group, his face as stoic as ever, but a new light glowed in his eyes. He then turned to Saitama and gave a formal bow.
"Thank you for your guidance, Sensei."
Saitama, who had been watching the whole process with mild interest, just shrugged. He patted the grimoire, which had now closed itself and gone blank again. "So it's an instruction manual. That's pretty useful, I guess."
He then looked past the stunned Black Bulls.
"Okay. Now, about that food…"