Thus, Rozen and Avrora formed an absolute contract, making Avrora his familiar.
Avrora then became a Beast Vassal, merged into Rozen's body, flowed into his blood, and was reunited with her eleven sisters.
That day, Rozen's blood burned with feverish heat from morning until night.
Because, with Avrora's return, the twelve Beast Vassals that the Fourth Primogenitor prided himself on had finally been fully restored.
As the saying goes, quantitative change leads to qualitative change—once all twelve Beast Vassals were gathered, Rozen distinctly felt their power unify into a complete whole, interweaving, resonating with one another—and suddenly, their strength surged dramatically.
It was as if the missing piece of a ring had been restored, forming a perfect loop of energy, causing all twelve to release triumphant roars, their powers skyrocketing.
That's when Rozen understood—
"This… this is the true power of the Fourth Primogenitor."
The complete power of the Fourth Primogenitor only truly manifested after all twelve Beast Vassals had returned.
Until now, although the incomplete group of Beast Vassals had shown tremendous strength, it was never their true full potential.
Only when all twelve were gathered could their real strength be awakened.
At that moment, this power was finally worthy of being called a god-slaying weapon—sufficient to destroy even Cain, the God of Sin, who wielded the Cleansing.
Now, Rozen had obtained the complete power of the Fourth Primogenitor, truly inheriting the power of both the Fourth Primogenitor and the God of Sin.
Unfortunately, the cost of achieving this was that Rozen's mana had once again been completely drained.
To reform the eleven Beast Vassals, grant them the ability to transform into human form, and summon all eleven at once—even without letting them use their powers—the mana cost was still staggering.
After all, vampire Beast Vassals were inherently mana-intensive beings, essentially solidified masses of mana.
Their mana demands were enormous. It's no wonder vampires were hailed as the strongest Demon race, each possessing extraordinary magical power.
And the Fourth Primogenitor's Beast Vassals were the twelve strongest of their kind, the pinnacle of all Beast Vassals. Just summoning one required immense mana—let alone twelve.
On top of that, Rozen had used Cleansing to sculpt their forms and grant them the ability to shift into human bodies—an additional cost that drained unknown amounts of power.
Because of all this, the mana Rozen had painstakingly accumulated was now squandered, and he would have to build it up all over again.
It was a harsh reminder of just how crucial mana was.
"I've got to hurry back to Chaldea and get Big Bro to help reconfigure my magic circuits."
With that decision made, Rozen no longer hesitated.
So, Rozen decided that in the next few days, he would leave Itogami Island alongside the royal family of Aldegyr.
When Rozen informed his friends of this decision, they were saddened, of course, but mentally prepared themselves to see him off.
However, when Rozen added that he would be taking Avrora with him, it sparked an immediate uproar.
Especially Himeragi Yukina.
"Why is Avrora allowed to go with you, but not me!?"
Yukina sulked for quite some time.
The others felt the same—they couldn't understand why Rozen suddenly chose to take Avrora.
Rozen explained it this way:
"Since the official story is that the Fourth Primogenitor's power inside me went out of control due to Cleansing, wouldn't it raise suspicion if Avrora—who shares a portion of that same power—were left next to Asagi, who now possesses Cleansing?"
In other words, Rozen was telling everyone:
If you're putting on a show, then commit to it fully.
Since the Fourth Primogenitor's power had supposedly gone berserk due to Cleansing, then from the perspective of the Management Cooperative, it would only be proper to place Avrora under supervision too—just like No. 12, who had lost control.
Additionally, taking Avrora away would help reduce unnecessary trouble.
After all, once Rozen left, many people would likely set their sights on the last remaining portion of the Fourth Primogenitor's power that was still outside—Avrora.
For these reasons, Rozen decided to take her with him.
This was Rozen's explanation.
Everyone thought it over, and ultimately, they had no choice but to accept it.
Even Akatsuki Nagisa, though deeply saddened by Avrora's departure, consoled herself by thinking it would only be a few months—not too long to endure.
Only Natsuki said nothing. She merely cast a long, deep glance at Rozen and Avrora, as though she had seen through something.
Thanks to this, Rozen's explanation was accepted. What was originally a farewell for one person had now become a send-off for two.
And once again, if you're going to put on a show, then do it right.
To fulfill everyone's final wish, Rozen, though reluctant to spend more mana, still summoned Avrora one last time so she could say a proper goodbye to everyone, especially to Nagisa.
To the people of this world, Rozen and Avrora's next return likely wouldn't take long. But Rozen himself knew: once he left this world and returned to Chaldea, who knew when he might come back?
Of course, no matter how long it took, when Rozen eventually returned, only a short time would have passed in this world.
That fact brought Rozen comfort.
And with that, Rozen finally relaxed.
No other reason—only because now, he had no more regrets.
Every world in which he had once left behind regrets—he had now made peace with them all.
Rozen no longer had any lingering attachments. He could return to Chaldea with a clear conscience, await the Spiritron Transfer to the Seventh Singularity, and begin the final stage of humanity's foundation—to bring salvation to the human order.
Rozen had nothing to fear.
Even if this final Singularity was the Age of Gods, the most difficult of all seven. Even if there existed an even greater threat than Solomon the Magus King within it, Rozen remained unshaken.
Not because his power had grown so much.
But because Rozen knew—he had to overcome this trial.
Only by doing so could he achieve the perfect ending and erase all regrets.
"This might be the final trial of my life."
And this trial—must be overcome.
"No matter who the opponent is."
Rozen steeled his heart.
And then, on the night before his departure—
A sudden quiver surged through his soul.
That tremor first caused Rozen to pause, and then his eyes lit up in realization.
Rozen murmured, both joyful and excited:
"So you've finally awakened?"
It had taken quite a while.
"My very first servant under an absolute contract."