Although the Manual of Ruthlessness could grant immortality, by then they would no longer be human. They would become emotionless machines—perhaps even more terrifying than machines without feelings. It was no surprise that demonic arts had such side effects, even those exclusive to women.
After much thought, Kael searched his mind and found a technique that wasn't overly evil, even appearing righteous. Practicing it could grant eternal youth, longevity, and even a holy aura—like an untouchable celestial maiden. But it had a fatal flaw.
It was actually a subsidiary art of the Heavenly Demon Technique, designed for furnace cauldrons. In simple terms, anyone who practiced it would be powerless before a Heavenly Demon inheritor, submitting completely, unknowingly becoming their plaything. This art was created by Heavenly Demon inheritors for their own amusement. They delighted in sending practitioners into the righteous path as pure maidens, only to publicly humiliate them by turning them into toys. Such acts dealt heavy blows to the morale of the righteous.
Seeing this, Kael sighed—demonic cultivators truly knew how to play. Their games were too twisted.
Just as he was about to pass this art to Marin and Saki, he changed his mind. Not because he feared they might encounter a Heavenly Demon inheritor. In this world, he was the only demonic cultivator—there was no second, nor any Heavenly Demon inheritor. Even if there were, it would only be him.
He changed his mind because this furnace cauldron art resembled a righteous technique, requiring spiritual energy from heaven and earth. But in this crossover world, despite the presence of spirits, yokai, and gods, there was no spiritual energy. Or rather, it was so scarce that cultivation was impossible. This was frustrating.
So even if he gave them the art, they couldn't practice it. To cultivate mana, they would need cruel demonic arts—like Kael's own, devouring souls and refining Flesh Pills. But would Marin and Saki follow such a path?
Impossible.
He knew they would never become true demonic cultivators.
Thus, most of the arts in his mind were unsuitable. The remaining female-exclusive arts were either yin-harvesting, draining essence, or manipulating emotions—not fit for Marin and Saki.
After searching thoroughly, Kael finally found a suitable art. "First, let me say—this ancestral technique can grant longevity, eternal youth, and ageless beauty. But it has one odd requirement."
Marin and Saki, upon hearing "eternal youth and ageless beauty," were already entranced, ignoring any oddities.
"Tell us quickly, Renjou-kun, please!"
For women, the promise of beauty was irresistible.
But Kael explained the drawback. "To practice this, you must drink my blood."
Marin and Saki froze.
"Drink your blood?"
"Why?"
Kael couldn't tell them the truth—that this art was also a subsidiary technique, like the Heavenly Demon and furnace cauldron arts. It was called the Blood River Divine Art.
He had considered it before—it allowed cultivation by consuming blood, opening a blood river within the body, achieving "as long as the blood river flows, I shall not perish." It was a unique form of immortality. But because it was too bloody, he had chosen the Soul-Devouring Art instead.
Now, however, he reconsidered. This art had one great advantage: once the blood river was opened, it granted near-immortality, greatly enhancing survival. It also contained a special secret technique—the Blood Puppet Method.
This was the art Kael intended to pass to Marin and Saki. The Blood Puppet Method allowed cultivation using Kael's blood. But in exchange, practitioners would fall under his control. If he wished, he could take everything from them—their life, blood, even cultivation. If he didn't interfere, they would notice nothing, living as normal cultivators. The only requirement was to drink his blood.
Thus, practitioners of the Blood River Divine Art always recruited others to practice the Blood Puppet Method. On one hand, these puppets served as blood reserves, available when needed. On the other, the art required vast amounts of blood, so helpers were essential.
Demonic cultivators were cunning and ruthless. To avoid poisoned blood, only trusted people could collect it. Blood puppets were ideal—they wouldn't dare betray, since their lives were bound to the master. Even if they tried, the master would sense it.
But Kael didn't reveal any of this to Marin and Saki. Instead, he gave a reasonable excuse. "The reason you must drink my blood is because my body is special. My ancestors were cultivators, so I inherited a unique bloodline. This bloodline can help others grow stronger."
Hearing this, Marin and Saki understood, even found it natural. Japan revered bloodlines and heritage. Politics, medicine, business—all were inherited. For commoners, without a good bloodline or background, success was nearly impossible.