Because La Folia and Kanon Kanase had moved in, Kaiser ultimately gave up his own bedroom for the two girls, who looked more like sisters than anything else.
There was no helping it—there were only three rooms in total. Other than Kaiser's bedroom, the other two had already been converted into a cat room and a computer room. Letting the two girls stay in either of those would've been… less than ideal.
Kanon had said she was fine sharing with the cats, but there was no way Kaiser was going to let the junior high saint live in the cat room.
So, he surrendered his bedroom, bought a bed to stick in the computer room, and moved in there himself for the time being.
Of course, Kaiser wasn't about to let La Folia and Kanon stay for free.
"Letting you stay for a while isn't out of the question—but there has to be proper compensation," Kaiser said.
What he wanted in return was knowledge of Aldegyr's Völundr System and Forged Holy Sword.
It was a tactical support system that could temporarily raise a weapon's spirit rank by infusing it with massive amounts of mana—strong enough to elevate even an ordinary weapon to holy sword level. Kaiser was more than a little interested.
If he could learn it and improve upon it, then in a pinch he could pour mana into his own personal weapons and drastically boost their power.
Since Kaiser's greatest reliance was his vast arsenal, a technique that could effectively raise a weapon's rank and class was extremely appealing to him.
That was why he didn't refuse their stay outright—and instead made such a request.
"…The Völundr System and Forged Holy Sword are the newest knightly equipment developed by Aldegyr—our most advanced and most powerful magic technology. And you want that just for letting us crash at your place for a while?" La Folia's gaze carried just the right mix of reproach to make even Kaiser feel a little sheepish.
It was true—asking for national-level classified tech in exchange for letting them use a bedroom was… excessive.
But Kaiser also knew that if La Folia simply needed a place to stay, she could find one without trouble. The fact that she, a princess, chose to crowd into his apartment meant she valued him for some reason—whether for political gain, recruiting him, or simply to have him nearby for protection.
And considering how curious she seemed about him, Kaiser knew exactly what was going on.
With that in mind, his conscience stayed clear.
"You don't have to give me every detail—just the method for raising a weapon's spirit rank. If you feel that's unfair, I can share some technology you might find useful," he said.
He then revealed part of his knowledge on artificial divine weapon crafting, which genuinely surprised La Folia.
"So you've been hiding this level of tech? You really are a treasure trove," she said, clearly intrigued.
While the data he gave wasn't overly complex, the concepts and techniques were fresh to Aldegyr—enough to potentially improve several types of magic-tech equipment and generate significant profits.
With that in mind, La Folia readily agreed, explaining in detail the principles and applications of the Völundr System and Forged Holy Sword.
Afterward, she added, "Basically, unless you're a daughter of the royal family, you need a spirit furnace to channel massive mana into the weapon. But you… I doubt that's a problem."
Her instincts were sharp—she'd already sensed the sheer immensity of Kaiser's mana.
It was a power surpassing even that of a God-Slayer by a hundredfold, and God-Slayers themselves were hundreds of times stronger than ordinary mages or sorcerers. In other words, Kaiser's spiritual power was tens of thousands of times greater than normal.
The mana of the Fourth Primogenitor was said to rival the dragon lines flowing through the earth—the vast ley lines themselves. And Kaiser's magic wasn't a whit weaker; if anything, it might be greater.
Which meant that even without borrowing power from spirits or a spirit furnace, he could meet the system's requirements with his own mana alone.
Still…
"I only want the technique for boosting a weapon's rank—not turning it into a holy sword," Kaiser said.
Aldegyr's Völundr System was paired with the Forged Holy Sword technique to raise their knights' weapons to holy sword level—granting them powerful weapons effective against demons, invaluable in their long wars with the Warlord's Domain.
But Kaiser didn't need that. If he wanted anti-demon capability, he could just pull out the True Longinus—holier and sharper than any legendary holy sword. A clean hit would drop even a Primogenitor on the spot.
What he needed was a pure rank-boosting method, which would be far more useful for someone with as many weapons as he did.
To master it, Kaiser inscribed the Forged Holy Sword spell formula into his spellbook—then began working with the Hōgyoku.
The Hōgyoku could absorb and manifest the will in its surroundings, shaping reality to match the heart's desire—so long as the wielder had the power to realize it.
Kaiser had systematically studied Kidō, understood magical theory from both divine weapon crafting and various other systems, and possessed the Dragon Head Jewel that boosted charm and luck, along with the spellbook from the god Ea, patron of wisdom and magic.
With all that, plus the Völundr System and Forged Holy Sword techniques, how could he not distill a pure weapon-rank enhancement spell?
The Hōgyoku simply sped up the process.
As a result, on the very day Kanon was discharged and moved in with La Folia, Kaiser succeeded in creating the technique.
To keep things simple, he still called it the Völundr System, but instead of producing forged holy swords, it purely boosted a weapon's rank.
He inscribed it into the spellbook, enhancing its potency and removing the restriction to mana—it could now be powered by any kind of energy.
Testing it brought satisfying results:
Orga Lux Weapons: up to double their power.
Longinus-type Sacred Gears: up to 30% increase.
Zanpakutō: up to 50% increase.
Divine Weapons: 40–70% increase depending on the item.
Weapons like the Ruyi Jingu Bang, Aymur & Yagrush, and the Trident could all gain over 50% more power. The Gungnir, Golden Sword, and Divine Sword of Salvation—likely due to their higher rank—maxed at 40%. The Ame no Murakumo was right at 50%.
The Type-100 Heavy-Weapon Demon-Slaying Blade "Silver Radiance Qilin" he'd obtained in this world was like a Orga Lux—able to double its power.
"Shame it only works on combat weapons," Kaiser noted.
Support-type gear like the Hōgyoku, Circle of Usurpation, Gorgon Stone, SpellBook, and the Bamboo Cutter set saw no benefit, nor could it be applied to biological weapons like Leviathan.
Still, as long as it was a weapon—even Longinus-type Sacred Gears like the Red Dragon Emperor's Gauntlet or White Dragon Emperor's Light Wings—it could be enhanced.
"Must be a conceptual technique—that would explain the rules," Kaiser mused.
He wasn't disappointed; boosting weapon power alone was enough.
With the Völundr System in his arsenal, his strength had taken another significant leap—though at this point, there wasn't anyone in this world worth going all-out against anyway.
"Still, a decent gain," he said, satisfied.
That night, in Room 705, a small celebration was underway.
"I don't know why Kanon and her family are living at your place, Kai-kun—but who cares! She's out of the hospital, so we're celebrating!" Nagisa Akatsuki declared, having shown up as if led by her nose, and single-handedly prepared a lavish spread to mark Kanon's discharge.
"…Why am I here again?" Kojou Akatsuki grumbled, clearly dragged over by his sister. But if he didn't come, he'd probably go hungry—so despite his sulking, he came. And the moment he saw La Folia, he froze.
"S-So pretty…" he muttered without thinking—only to get smacked by Nagisa on the spot.
"Don't ogle Kanon-chan's family, Kojou-kun. If you embarrass the Akatsuki name, I'll make sure everyone at Saikai Academy laughs you out of the building!"
Given her infamous big mouth, the threat carried weight—and Kojou immediately went ramrod straight, focusing solely on his food, not daring even a stray glance.
What he didn't know was that the moment he'd entered Kaiser's apartment, the Holy Ring Knights guarding La Folia and Kanon had run a complete background check on him—including the type of "hobby magazines" he kept. Had he actually offended the princess, he'd be famous across Saikai Academy—and all of Itogami Island—by tomorrow.
So Nagisa's warning had, ironically, saved him.
The little party went on until past midnight, finally winding down when the Akatsuki siblings left and the lively mood faded.
Kaiser set his cats to cleaning up, while La Folia and Kanon went to bathe.
"…How am I supposed to have any privacy like this?" Kaiser muttered in the living room, feeling that familiar prickle of being watched.
It wasn't an enemy—it was the Holy Ring Knights, either hidden inside the apartment or in nearby buildings, keeping constant watch. It was understandable—they were protecting two princesses—but it was still irritating.
If he hadn't already struck a deal with La Folia and collected payment, he'd have complained by now.
"Forget it. Out of sight, out of mind."
He left the living room, returning to the computer room where his bed was set up, and lay down to sleep.
The windows were shut, so no one could spy from outside. Feeling secure, Kaiser was just about to close his eyes when a soft, hesitant knock sounded at the door.
"Who?" he called warily.
Could it be that scheming princess up to something again?
But then, an unexpected voice answered.
"It's me—Kanon." Her gentle, shy tone came through the door. "Senpai… are you asleep?"
"Kanon?" Kaiser blinked. "Come in—it's not locked."
The door opened quietly, revealing a silver-haired figure.
"Sorry to bother you, Senpai," Kanon said with a polite bow.
She'd changed out of her uniform into a knee-length nightdress of soft blue fabric, matching the icy blue of her eyes. A faint mist still clung to her skin, and her hair was damp—clear signs she'd just stepped out of the bath.
Looking at her, Kaiser frowned slightly.
…What's this girl up to?