If someone were able to peer inside Aize's body, they would discover glowing golden patterns etched throughout him.
These golden lines flickered between brightness and dimness—sometimes dazzling, sometimes dull—as if alive, pulsing rhythmically like a heartbeat.
They extended across every part of Aize's flesh and organs, completely fused with him.
No—more accurately, these patterns were not foreign elements at all. They were possibilities that had originated from Aize himself, only awakened by the Fantasy Library. They were inseparable from him, fundamentally one with his being.
At the very moment Aize grasped the Black Furnace Demon Sword, those golden patterns that ran through every corner of his body suddenly burst into radiant light.
Clang!
Golden lines appeared on the hand gripping the Black Furnace Demon Sword, resembling golden blood flowing into the blade. The same golden patterns etched themselves onto the sword's surface.
Buzz!
The Black Furnace Demon Sword suddenly trembled. Its pure white blade emitted a terrifying heat, releasing a wave of scorching air that surged through the entire testing chamber.
"What…?!"
On the other side of the glass, the lab personnel in white coats, who had been working in an orderly fashion, immediately panicked.
"What's happening?"
Claudia's expression also changed in shock, and her hand tightened around the holster at her waist.
It couldn't be helped. In that instant, not only did the Black Furnace Demon Sword undergo an abnormally strong reaction, even Claudia's Pure Starflare-type weapon trembled violently.
A wave of violent heat swept through, dyeing the entire lab in crimson and distorting the air with its intensity.
The temperature in the area rose at an alarming rate, turning the surroundings into a massive furnace.
"Is it out of control?!"
"These numbers are off the charts!"
"The heat has exceeded the critical threshold! This—this is a value we've never seen before!"
"Activate the defensive barriers, now!"
The staff behind the glass frantically operated the instruments, causing transparent barriers to rise around the test site.
All the heat was contained within the barriers, isolating even Claudia on the outside. Only Aize remained inside, holding the blazing Black Furnace Demon Sword. His clothes were billowing, his entire body at the eye of the scorching storm, his figure blurred by the heat-distorted air.
Because of this, no one present noticed the golden patterns on Aize and the Black Furnace Demon Sword. Only the sword itself seemed fully aware of the transformation, releasing immense heat. The all-purpose substance surrounding it formed dark patterns that flowed along the blade, finally infusing the crimson All-Purpose Core Crystal, making it glow an even deeper red.
At that moment, the pure white blade of the Black Furnace Demon Sword, under the intense heat, turned completely black.
The blade of the Black Furnace Demon Sword was originally formed by the condensation of immense heat.
It could easily burn through anything and melt steel. Now that its heat had intensified even further, the demonic sword had finally taken on the pitch-black appearance that matched its name. Its output power now surpassed any level it had ever reached before.
Such astonishing heat and high temperature would be unbearable even for members of the Starvein generation. If anyone got too close to the demon sword, they might even be melted on the spot.
Yet Aize, standing face-to-face with this terrifying heat, remained completely unharmed. His hand gripped the Black Furnace Demon Sword steadily, and he hadn't even broken a sweat.
He simply stared at the Black Furnace Demon Sword, now mere inches away, and attuned himself to its will.
In his perception, the Black Furnace Demon Sword, which had earlier lost interest in him, now seemed to awaken suddenly. At first, it responded with emotions of confusion and panic. Then it turned its attention back to Aize, as if recognizing something unbelievable, something shocking—its feelings shifting from doubt and astonishment to joy, delight, and finally, fervent devotion.
It was like a loyal subject laying eyes on its sovereign.
Then, the golden patterns flowing from Aize's hand surged into the Black Furnace Demon Sword at full speed.
Not long after, those golden patterns completely covered the sword's entire body. They flickered between bright and dim, dazzling and dull, until they eventually formed an extremely intricate and mysterious geometric pattern. This mark etched itself onto the red All-Purpose Core Crystal of the Black Furnace Demon Sword and sank into it.
At that moment, the ultimate authority over the weapon was fully activated.
The Black Furnace Demon Sword recognized Aize as its sole master—something it would only do once in its entire existence—becoming his very first personalized weapon.
"Beep, beep—"
Within the testing chamber, the display window that showed compatibility rates started emitting sound effects as the value soared upward.
Seeing this, the staff in white coats were stunned.
Before their eyes, the compatibility rate, which had originally been only 8%, shot up at an astonishing speed, quickly surpassing the 80% threshold required by the Star Guidance Academy to permit borrowing Pure Starflare-type weaponry.
The number kept rising until it hit the maximum value of 100%. Then, amid blaring alarms, it turned into a chaotic string of garbled code.
Witnessing this, not only was Claudia utterly stunned—the lab technicians were also left slack-jawed, one after another.
"C-Compatibility rate... unmeasurable!"
One technician stammered out the report, voice trembling.
"He's broken the upper limit!"
The theoretical maximum compatibility rate was unquestionably 100%.
But now, someone had broken that ceiling.
The Black Furnace Demon Sword—one of the top-tier weapons among all Pure Starflare-type armaments—had remained unused for years. Like the other three elemental demon swords, it was infamous for being nearly impossible to master.
Now, not only had someone obtained it, but their compatibility had surpassed the very limits of measurement, reaching a height never before seen!
"Buzz!"
The energy blade, formed by transmuted All-Purpose Substance, vibrated and let out a resonant hum.
Aize lowered the hand that had been holding the Black Furnace Demon Sword aloft. Looking at the Pure Starflare-type weapon, now radiating a will of submission, a smile slowly appeared on his face.
Inside the test chamber, the overwhelming heat began to subside, and the scorching air gradually dispersed.
"Let's get along from now on, Black Furnace."
That soft murmur, laced with a quiet laugh, faded along with the dissipating heat—accompanied by Claudia's complicated gaze from afar…
...…
Top Floor of the High School Building — Student Council Office.
"Is that everything, President?"
Aize handed the final signed document to Claudia, who was seated behind her desk.
"Yes, that completes all the procedures."
Claudia took the document, her gaze fixed on Aize, as if trying to see through him, while wearing her usual calm and composed smile.
"When will I be able to receive the Black Furnace?"
Aize casually asked the question.
"Once the Equipment Bureau finishes the final calibration and inspection of the Black Furnace Demon Sword, it will be handed over to you, Aize."
Claudia answered truthfully.
Although quite a few unexpected things had happened earlier—including the outrageous event of someone breaking through the compatibility limit—after deliberation, the academy ultimately approved the loan of the Black Furnace Demon Sword.
No doubt, they were eager to see just what kind of power someone could unleash using a Pure Starflare-type weapon that had exceeded the compatibility threshold.
After all, collecting usage data was the entire purpose behind lending Pure Starflare-type weapons to students in the first place.
So, Aize had successfully acquired the Black Furnace Demon Sword and now possessed a Pure Starflare-type armament. It would only be a short while before it was formally handed over to him.
Of course, if Aize wished, he could summon the Black Furnace Demon Sword right now.
It had already become his exclusive weapon, able to be called into his hands at any moment.
Others believed that Aize had merely been granted the temporary use of a Pure Starflare-type weapon, but in truth, that weapon now bore his name.
Naturally, Aize had no intention of revealing this fact.
Claudia, unaware of this, still felt a mix of emotions.
Even she hadn't expected that Aize would truly obtain the Black Furnace Demon Sword.
"The future… has been changed."
Claudia murmured to herself.
"What was that?"
Aize didn't quite catch her words and looked at her in confusion.
"It's nothing," Claudia quickly shook her head and smiled nonchalantly. "The Black Furnace Demon Sword is an incredibly powerful Pure Starflare-type weapon, but it's also famously difficult to control. I hope you'll be able to wield it responsibly."
Upon hearing that, Aize nodded and smiled.
"I will."