Rozen had already speculated about the "mistake" that Harutora spoke of.
Now, the whole world knew that Yakou had used the Taizan Fukun Ritual to connect with the high-ranking spiritual entity known as Taizan Fukun, borrowing divine power to reincarnate into this era as Tsuchimikado Harutora.
But why exactly did Yakou choose to reincarnate in this era?
Was it merely for the sake of studying jujutsu? Or was it simply a desire for rebirth?
Of course not.
It was well known that the reason Yakou performed the Taizan Fukun Ritual was because, during the Pacific War, the former empire had reached a desperate situation. To reverse Japan's impending defeat, Yakou, as the highest authority of the Onmyo Agency, was ordered to conduct a grand jujutsu ritual to repel foreign invaders.
Thus, Yakou carried out the Taizan Fukun Ritual, but in the end, it failed—leading to frequent spiritual disasters in Tokyo and making him the greatest criminal in jujutsu history.
That was the commonly accepted story.
But here was the real question:
Half a century ago, how exactly did Yakou intend to use the power of the Taizan Fukun Ritual to resist foreign invaders?
The answer was not difficult to guess.
Since the Taizan Fukun Ritual was a jujutsu technique that manipulated souls, and considering the war situation at the time, if Yakou chose to use this grand ritual, the logical conclusion was that he intended to summon a powerful deity to fight against foreign armies.
And that deity was undoubtedly a divine spirit.
Only a divine spirit could have single-handedly reversed the fate of a nation in such circumstances.
Moreover, considering that Kurahashi Clan and Souma Clan assisted Yakou at that time, it was not hard to imagine that the idea itself originated from them.
In other words, Yakou was once a collaborator in Kurahashi and Souma's divine descent plan.
This was why the Kurahashi and Souma clans had been desperately searching for Yakou's reincarnation—to restore him to his rightful place and perform the divine descent ritual once again.
Unfortunately, the ritual had ultimately failed.
Rozen stared at Harutora and slowly spoke.
"Tensou Jifu Ritual."
As soon as those words left Rozen's mouth, the entire atmosphere changed.
Harutora's face darkened.
The others were stunned.
Even Natsume, who was still struggling in Tamamo-no-Mae's grasp, was astonished.
"Tensou Jifu Ritual?" Natsume exclaimed. "Isn't that the most secretive ritual of the Tsuchimikado Clan?"
Indeed.
The Tensou Jifu Ritual was the Tsuchimikado Clan's most sacred and secretive ritual—a higher-level version of the Taizan Fukun Ritual.
- Tensou referred to the gods of the heavens.
- Jifu referred to the gods of the underworld and the officials of the afterlife.
If the Taizan Fukun Ritual was a ritual to worship Taizan Fukun, then the Tensou Jifu Ritual was a grand ceremony to worship twelve deities, including Taizan Fukun, making it the most important ritual in Onmyodo.
Like many other jujutsu rituals, this ceremony was abolished during the Meiji Restoration, and it was around this time that the Tsuchimikado Clan began to decline.
However, Yakou had revived many lost jujutsu techniques with his unique interpretations, and within his Imperial-style Onmyodo, the Taizan Fukun Ritual existed—leading many to speculate that he had also revived the Tensou Jifu Ritual.
In reality, the ritual had indeed been revived.
This was something Rozen could confirm with absolute certainty, having inherited all of Yakou's knowledge on jujutsu.
"That wasn't the traditional Tensou Jifu Ritual passed down by the Tsuchimikado Clan."
Rozen stated the truth.
"It was a modified version—just like the Taizan Fukun Ritual—a new, Imperial-style Tensou Jifu Ritual created by your past self."
Originally, the Taizan Fukun Ritual was merely a ceremony for communicating with spirits, but under Yakou's modifications, it became an Imperial-style jujutsu, allowing the user to manipulate souls freely.
The same applied to the Tensou Jifu Ritual.
Originally meant as a ritual to worship multiple deities, Yakou had transformed it into a forbidden jujutsu that summoned gods.
"If my memory is correct, your past self specialized the modified Tensou Jifu Ritual to summon only one specific deity."
Rozen spoke with absolute calm.
"That deity is the ancestral god that the Souma Clan has been trying to summon for centuries."
Since the Tensou Jifu Ritual was a ritual to communicate with gods, Yakou had combined it with the Souma Clan's hereditary divine summoning techniques, ultimately turning it into a ritual solely for summoning the Souma Clan's ancestral god.
And in the past, Yakou performed this ritual to protect the nation—but the attempt failed, causing Tokyo's spiritual landscape to change drastically, leading to the great spiritual disaster and countless subsequent calamities.
This was why Yakou chose to reincarnate in this era.
"The failure of the ritual must have left you on the verge of death. And you knew that the Souma Clan would one day attempt the ritual again to summon their ancestral god. That's why you used the Tensou Jifu Ritual to cast a similar Taizan Fukun Ritual on yourself—reincarnating into this era to stop the divine descent plan from happening again."
That was the mistake Harutora had been talking about.
Because the divine descent ritual failed, Harutora's past self became one of history's greatest criminals, causing the Tokyo spiritual disaster and leaving the land plagued with misfortunes.
Now that he had returned to this world, it was inevitable that he would try to stop it from happening again.
After all—
"The Tensou Jifu Ritual used exclusively for summoning the Souma Clan's ancestral god came from you—and now, it has fallen into the Souma Clan's hands."
Rozen sighed.
"Given that they've possessed this divine summoning technique, the Souma Clan—who have been preparing for this for over a thousand years—would never miss the opportunity to try again."
If the Souma Clan successfully used the ritual that Harutora's past self had created, leading to catastrophe, how could Harutora possibly sit back and do nothing?
It was only natural that he would want to stop it.
However—
"Did you ask the wrong person?"
Rozen let out a sigh.
"You do realize that I have no reason to stop any of this, right? Because I did the exact same thing as you and the Souma Clan."
In the past, during the summoning of Kinu and Gyokuto, Rozen had also borrowed knowledge from the Tensou Jifu Ritual. If not for the Crimson Wing Formation assisting him—and the fact that he possessed complete knowledge of divine summoning—his own ritual might have ended in failure, resulting in a catastrophe no less severe than Yakou's.
Therefore, Rozen truly had no grounds to interfere.
If he did, then in the struggle between Harutora and the Souma Clan, he wouldn't be a mere observer—he'd be taking sides.
Even now, Rozen had no intention of getting involved.
"I and your past self only differ in one way—one succeeded, the other failed. Given that, if the Souma Clan's divine summoning fails, I might clean up the mess. But if they succeed, what reason do I have to stop it? Wouldn't that be the same as denying everything I've done?"
For this reason, Rozen had returned only to retrieve Natsume and Suzuka and, if possible, to ensure the Onmyo Agency stopped pursuing the Tsuchimikado Clan, allowing them to walk under the sun again.
Beyond that, he had no other plans.
As for the Souma Clan's divine descent—he would only observe.
Unless—
"Do you know which god the Souma Clan is trying to summon?"
Harutora asked, eyes sharp.
"Of course."
Rozen answered calmly.
Then, he uttered a name.
"It's Taira no Masakado, isn't it?"