The Imaginary Tree—a specialized conceptual structure and hypothesis.
In a broad sense, it can be defined as the collection and evolutionary structure of "existence" itself.
In this hypothesis, the trunk represents the continuity of "reality" and the irreversible flow of time, while the infinitely branching limbs correspond to parallel worlds that exist based on divergent possibilities. These worlds are further categorized into "World Bubbles" or "Divergent Timelines" based on whether they can continue to grow from the foundation of the "present."
For any determined "present" world—an observation point located at the tip of a specific branch—the path of that branch is the only reality.
At the divergence nodes closer to the trunk, the branches that were not "chosen" and instead extended in other directions may have briefly existed within the imaginary topology based on "possibilities" at the quantum or macroscopic level. However, to an observer in the current world, they belong to the "discarded set of possibilities."
While their informational states can theoretically be traced, their materialized and realized physical existence is generally considered unreachable and impossible to merge back into reality due to the differences in "existential anchoring" and the existence of "temporal-causal barriers."
The unconventional nature of the Authority of "The Past" lies in its ability to briefly bypass the absolute rejection of "existential anchoring" under specific conditions.
Thus, it can "project"—or even "temporarily graft"—historical fragments or shadows of possibilities from other divergent branches onto the neighboring imaginary coordinates of the current world with high fidelity. This isn't a permanent change to the foundation of the timeline; rather, it's like superimposing a brief, stable "holographic patch" from another possibility onto the "information" of the current world.
However, even a "graft" of this magnitude is not something a single Herrscher's authority can achieve under normal circumstances.
It requires two critical conditions.
First, there must be a "structural wound" or "loosened anchor" in the current world deep enough to touch the level of existence itself. The "superposition state" of Chen Tianwu and Anna was precisely such a rare gap that tore through the stability of local existence.
Second, it requires energy far exceeding that of a standard Herrscher, as well as a "sublimation" where the authority breaks through its inherent limits.
That is to say—the False God status.
Only by ascending to the state of a False God can one forcibly complete the extraction of corresponding information and anchor it.
And the previous Herrscher of the Past, Yunmengxi, at the cost of her total dissipation, burned everything to obtain this fleeting miracle. Just like the final carnival of the Herrscher of Desire or the extreme breakthrough of the Herrscher of Theory—
Before she completely vanished, Yunmengxi ascended to the False God state for a single Planck time interval.
It was, in every sense of the word, "a single moment."
Therefore, the feat of "The Past" was highly incidental and irreproducible. Even if another individual existed whose authority or energy level was highly similar or identical to "The Past," they could almost never recreate this feat.
The reason lies in the fact that any attempt to "replicate" the act would carry the "informational residual" unique to the operator's own existence. These "extra factors" would act like tiny impurities falling into a chemical reaction that requires absolute purity, destroying that fleeting, delicate balance.
This was no longer a matter of technology. This was "uniqueness" and "irreplaceability" at the existential level.
Even if another Herrscher of the Past, or Yunmengxi herself at another point in time, tried in a different way, they would be destined to fail because the specific combination of "time," "space," "momentum," and "self" could not be recreated.
...
But aside from the fact that "The Past as imitated by Shu" had five more words than "The Past," leading to different information entropy, Shu could perfectly replicate the remaining "time," "space," and "momentum."
And now, the final condition, "self," had been met...
What could Shu do?
Or rather—
What could this Core of the Past, Yunmengxi's final gift, do?
...
It was a Regret Pill!
It could truly allow you to return to the "past" to change something, and then the world would modify the "present" based on your changes in the past. Thus—your "now" would become the "better future" that the past version of yourself had envisioned!
The price was merely the sacrifice of a Herrscher's entire being, and the requirement that the world happened to have a suitable crack.
And he... Shu...
He...
Did he have anything to regret?
...
If "The Past" could graft one ARC City, then theoretically... could it graft a second... a third?
Those cities that died the instant the Great Honkai descended... that 99.99% of the population that was wiped out the moment disaster struck...
Those "pasts" already buried by time, sentenced by the iron laws of "reality"...
Could they all be pulled back?
It could be done!!
As long as he had the core, as long as he understood the authority!
As long as those who followed could find a suitable "wound" in the world or create one, as long as they could replicate that miraculous burst of energy and sublimation of authority...
...No...
That wasn't right.
That wasn't what he wanted to do...
Shu thought he had long since grown accustomed to thinking with "the big picture" in mind. Sacrificing the minority to save the majority, weighing pros and cons, choosing the optimal solution... he thought his heart was hard enough, his vision long enough.
But when a tangible "Regret Pill" was placed before him, what crashed through his rational defenses was a "trivial" little thing.
Did he... have anything to regret?
Shu stared at "himself," questioning his soul.
Then—
His trembling pupils suddenly contracted to their limit.
—How could he not have regrets?!!
The chaotic Chiba Academy shelter. Otto's unsettling "asylum."
Followed by the fall of the shelter and the flight.
The panicked crowds, the collapsing ruins, the agonized cries.
And that desperate command—
Head for the military base... once we get there, we'll be safe...
Safe... was it?
No...
That place was hell.
Shu still remembered the swarms of Chariot-class Honkai beasts that covered the sky. He remembered the fire he caught out of the corner of his eye as the trucks turned around.
He remembered. He remembered all of it.
He remembered it even more clearly than Kiana, who blamed herself for it!
If his past self had possessed the powerful strength he had now...
If his past self could have seen as far as he did now...
If his past self had possessed the resolve to save the world that he had now...
If...
If his past self hadn't feared death, hadn't wanted to flee... if his past self could have "died" one more time for those people he had only met once!
—
It was the haunting thought of: "I could have."