The Main World—let's call the everyday world where Homura has been reborn for now the Main World.
Originally, this was a completely mundane everyday world, so ordinary that even slice-of-life shows like Dragon Maid or the lazy angel Gabriel, or all those comedic dailies with superhuman powers, weren't allowed to exist. It was a truly everyday world.
At best, it just had a bunch of everyday anime heroines that Homura recognized. Ignoring those familiar faces, in terms of physical laws, it was no different from the Earth of his previous life. Treating it as a parallel ordinary Earth was no problem at all.
But the Crimson Denizens that had appeared now were clearly not something that should exist in this world.
They were foreign intruders—!
...
Roughly twenty years ago, around the time Homura descended into this world, the entire sea of worlds seemed to be influenced by some force and began to converge.
With the Main World where Homura resided at the center, the surrounding universes—ones that were originally completely unrelated, each running on entirely different worldlines—started drawing closer to the Main World.
And when worlds draw closer, collisions become inevitable. Even channels between worlds might open, allowing species from both sides to cross over to the other.
The clash of diverse species would inevitably spark brilliant fireworks.
The first universe to collide with the Main World was the High School DxD World. Fortunately, it only cracked open a tiny seam at the time, letting two weak stray low-class devils slip into this world.
The world will—or rather, the Gaia will of this world—instinctively awakened in that moment.
It had no self-awareness, merely following instinct to exterminate the pests. Before those two devils could cause a huge commotion, the world will preemptively guided several beings from its own universe—ones with extremely strong luck and combat potential—to eliminate them.
Low-class stray devils were stronger than humans, but not to the point of completely ignoring modern firearms. Even so, they had some unanalyzable tech-defying tricks up their sleeves, which still led to those few highly fortunate beings perishing in a mutual destruction.
There was no such thing as "protagonists with heavenly luck" in this world. At most, it was just individual fortune—like the original male and female leads Homura knew of, who did have luck far superior to ordinary people. So even when those plot protagonists encountered inhuman monsters or dangers beyond their power, they still died.
After resolving this crisis, the world will finally noticed the other universes constantly closing in. For the first time, it became aware of truly different worlds beyond its own worldview. After absorbing a massive amount of information from the High School DxD World...
Realizing how weak its own world was, the Main World's world will began its instinctive self-rescue—!
Collisions with other worlds would happen sporadically in the future. If powerful gods or demons discovered it before the world could repair its seams, no one knew to what extent outsiders would wreck this place.
Thus—the Main World Will sent out an SOS distress signal to the entire sea of worlds.
It was just a world without any mystery—even if it struggled, it couldn't go from zero to one, conjuring up powers for its humans out of thin air.
Thus—the Main World initiated an alliance with all the other converging universes that didn't want to be invaded or influenced by their neighbors. After paying a certain price, it successfully applied for the first batch of power loans, borrowing strength from other worlds to help nurture its own "young ones." Once those young ones grew strong enough, they could protect the world they inhabited.
Thus—
Homura's golden finger was born! Cheat activated!
So—he finally understood what that light orb inside him was. That's right, the light orb—!
In the moment of crisis, a small light orb had suddenly popped out inside him and transmitted all the information to him. And this light orb was precisely the Powa (power) that the Main World Will had obtained through its loans from other worlds!
By resetting the worldline, it consumed parts of its universe's beings with powerful luck and fortune (limited to male leads under narrative causality) as materials to craft the light orb. This created the strongest fortune ever—an unprecedented, rule-breaking level of super-world-class luck—mixed with a cheat assembled from all the loaned powers from other worlds.
With the strongest luck and the loaned powers, as long as one adapted a bit, they could quickly become a powerhouse.
Originally, this light orb was meant to be tossed to the only remaining being with relatively strong luck—the host named Yagami Taichi.
But during the world will's formatting process earlier, it accidentally formatted Yagami Taichi along with everything else.
Without the specially selected host—someone brimming with infinite courage, who could muster the bravery to save the world even knowing the scale of this super-world-class catastrophe—the world will, which had no autonomous consciousness and only instincts, crashed.
Thus—
The cost of the crash was a broken-jar-falls-hard mentality, like it might as well pick someone at random to be the savior.
The light orb was randomly tossed to Odaiba Elementary School, where Yagami Taichi's protagonist group would have been born, and it just happened to land on the whistle hanging on Yagami Hikari's chest.
Homura, thanks to his naturally powerful mental strength—even before awakening or recalling the Digimon plot—subconsciously felt an inexplicable fondness for Yagami Hikari and the others when he saw them as a kid. Back then, he'd fantasized about being one of the chosen children too! His favorites were the Yagami family.
Whether it was Yagami Taichi with his exceptional leadership and boundless courage paired with the cool WarGreymon, or the sweet and adorable Hikari with her beautiful childhood goddess Angewomon, he loved them all.
So while kids his age preferred playing with older ones and shunned those younger than them, little Homura loved taking Hikari along to play. From then on, he had a little tag-along who was even younger than him trailing behind.
And as is common with kids in daily life—especially otaku ones—they mature pretty early.
Homura had accidentally flirted with Hikari as a kid, and after her family was forced to move away due to circumstances, she never forgot him. When she left, her eyes were swollen from crying, and right before parting, she gave him her beloved whistle.
Homura wore it for years afterward, until one day it was directly absorbed by the light orb, making the whistle vanish.
Because of that—kid Homura felt guilty about it for a long time—!
...!!
Holy crap, no wonder I couldn't find my whistle—it got sucked into my body all along.
Wait, that super-world-class crisis... it couldn't be related to me, right?
It lined up perfectly with the timeline of my arrival in this world, and for some reason, the surrounding universes were converging on the Main World instead of any other—Homura felt a twinge of inexplicable guilt for a second—!
Overthinking things beyond human control wouldn't do him any good.
As the price for gaining power—the ticket to the path of strength—he had to become the savior!?
Whatever—!
With such a powerful golden finger and knowledge of so many plots, if he didn't have the confidence and courage to crush everything, he'd truly be a loser!
These twenty years of training as the Saigo Family heir weren't for nothing!
Only by mastering power in his own hands could he feel at ease. Saving the world was just a side gig.
Now that he had the power to defy fate, Homura had fully regained his composure and calm. As long as he had a chance to fight back, even with ordinary abilities, if he could take the reins, he feared no challenge.
Sure, he couldn't reach monster levels like genius-IQ demons or body-freak grass monsters among humans. But in reaction speed, thinking, stamina, combat skills—all those things that could be trained postnatally—he, having undergone specialized family training, far surpassed those ordinary protagonist types.
Now, with the same treatment as those protagonists—or even more exaggerated—the strongest super-world-class luck, even if he got some support-type power, as long as it had a bit of combat utility, he could...
Anyway—first things first, time to draw a Powa!