The two fought for a full day, and neither side could do anything to the other.
Unohana Retsu's speed was very fast, and Rias's attacks were hard to land effectively.
Unable to engage in close-quarters combat and with her magic power attacks failing to hit, she could only find ways to use her magic power more efficiently.
The full day also allowed Rias to gain a lot.
In particular, turning the grimoires she had read in the past into her foundation accelerated Rias's growth.
"Huh."
As the blade swept past, a trace of blood appeared on Rias's cheek.
Touching it with her finger, Rias said with some surprise, "I'm actually injured?"
"Your stamina has dropped."
Unohana Retsu didn't continue her attack, but instead said, "Although you still have quite a bit of energy in your body, the stamina required to command this energy isn't enough to face such a long battle."
In a day's time, Unohana Retsu had also come to understand this girl.
Refining her Magic Formulas mid-battle, experimenting with her power, and constantly memorizing the combat to turn it into nourishment for her growth.
She was awe-inspiring and beautiful during battle, as well as incredibly pure, yet she wasn't a battle maniac.
Compared to her magic power, manipulating such power required extreme control, which to some extent exhausted her spirit.
"I see."
Rias nodded slightly and then said, "Then let's decide the winner with one final blow."
"A final blow, huh."
Unohana Retsu showed a look of anticipation.
"Yes, one final blow."
Rias gave a charming smile, causing a bad premonition to rise in Unohana Retsu's heart.
"It's said that Yamamoto Genryūsai Shigekuni's Zanka no Tachi possesses the power to destroy the world."
Rias smiled and said, "And I have a similar move, though this one requires accumulating magic power in advance."
"Formula Seven: Heavy particle destruction missile!"
After saying that, Rias opened her hand, and a dark red sphere-like object fell.
In an instant, the dark red spherical object collided with the ground.
Accompanied by a thunderous roar, a massive dark red mushroom cloud rose into the sky.
In an instant, the outcome was decided.
Just as atoms have Nuclear Fission or fusion reactions, in Rias's research, magic power also possesses the same characteristics.
Using this as a basis for her research, Rias stored up a large amount of Power of Destruction.
Igniting it when needed, it would begin to fuse under the effect of the Fusion Equation, instantly releasing a massive amount of destructive energy.
The method of fusion was the path to becoming a Transcendent that Rias had created herself.
Ajuka's Kankara Formula, Sirzechs's Devils True Form, and the fusion of the sun.
If the Fusion Equation created by combining these three could be maintained stably, she could surpass Sirzechs in one fell swoop, perhaps even reaching a level comparable to Shiva or the God of the Bible.
As for Sirzechs's Devils True Form, that was magic power on a completely higher level; just touching his body could turn all things into nothingness.
Sirzechs's Devils True Form consists of high-density Power of Destruction, which is why he possesses strength within the world's top ten.
After all, the Devils True Forms of other Devil Kings, including Vali Lucifer, consist of twelve devil wings, while only Sirzechs is special—his Devils True Form is a magic power reaction.
"The explosion is quite beautiful."
Rias remarked with a sigh.
This wasn't the first time Rias had used this move; the magic crystals she gave to Jibril were condensed using the method of fusion.
It could be considered an achievement in'stable magic power fusion'.
However, this kind of one-time explosive fusion was being released for the first time.
Ephemeral Beauty!
At this moment, Rias covered the surface of her body with a layer of magic power of the same nature, thereby assimilating the external magic with her own so she wouldn't be harmed.
Of course, this was also because the destructive energy itself belonged to her.
The light, seemingly substantial, swallowed everything whole; it was a strategic magic developed entirely by an individual.
The battle ended, and the air shimmered with the residual fluctuations of Power of Destruction.
If not specially treated, it would likely remain here for several years.
"And as expected, is it a lack of quality? The fusion didn't collapse inward at the end to form a Supernova Explosion."
In a way, this move isn't perfect yet, haha~
A minute later, the Arena dissolved, and Rias's attention returned to the main world.
She glanced at the time; it was still the same time as when she had opened the Arena.
But her spirit was already very exhausted.
At the same time, the strategic weapon she had accumulated, the Baryon Bomb, had not been consumed.
It seemed the Arena projected one's state, including all weapons, into the Arena for combat.
Simply nice!!
Unohana Retsu: "That move of yours is too dangerous; it's completely different from Zanka no Tachi."
"My brother's Devils True Form can transform his body into a stable, high-density destructive energy body. Isn't that very similar to Zanka no Tachi?"
Rias responded.
Zanka no Tachi is essentially a high-density condensation of flames, without a fusion reaction.
In a way, the two are indeed very similar.
But it's only a similarity.
The power levels of both sides might be the same, but Sirzechs is clearly stronger.
Yamamoto Genryūsai Shigekuni's body was a weakness, and because of that, he died in the Thousand-Year Blood War.
Unless Yamamoto Genryūsai Shigekuni could, like Aizen, fuse himself with his Zanpakutō, becoming an energy body comparable to the temperature of the sun's core at any time and controlling it stably.
Otherwise, he couldn't possibly be a match for Sirzechs.
Even so, there's a gap in the quality of the energy.
The difference between Yamamoto Genryūsai Shigekuni and Sirzechs isn't just a little; it's an entire major realm.
"..."
Unohana Retsu: "It's only a similarity; the essence is completely different!"
"The Ephemeral Beauty of that moment... so beautiful, truly too beautiful!!"
Jibril: "I really want to learn it! Get me one too!!"
Rias said, "This move is a bit more expensive because it already involves the core of my Hakai Hōteishiki."
Jibril: "Name your price."
Not to mention converting all the properties of her body; that would be extremely difficult for Jibril, equivalent to transforming herself into an existence similar to the Elementals.
Jumping directly from Sequence Six to Sequence Three is simply more difficult than Rias becoming a Transcendent.
Jibril's strength is estimated to be at the level of a Transcendent already, and her Heavenly Strike can reach a Dragon God Level attack.
If a fusion reaction were added to it, this move could completely undergo a qualitative change!
Rias: "The manufacturing method of the Flugel, including its core Magic Formula."
"!!!"
Jibril: "Hey now, this isn't a joke~"
"I'm not joking either."
Rias said, "This move already involves the core power of two of our Transcendents, as well as my essential Formula. If completed, the intensity of every Flugel's Heavenly Strike will undergo a qualitative change."
"Furthermore, I've only completed the first stage of this move. The second stage is a completely stable Magic Formula that can be applied to oneself to produce higher-quality spirit energy. The third stage can even transform oneself into an energy body. For both you and me, this value far exceeds my requirements."
"..."
Jibril: "Let me think about it."
Although Jibril had no taboos and even thought of overwriting her own core Magic Formula to kill a Dragon-kin with a self-detonation during the Great War.
But trading the core Magic Formula and manufacturing method of the Flugel is already equivalent to betraying the Flugel.
Even though Rias is a person from a Other World, it is indeed a difficult decision to make.
Rias: "If you master the third stage of the Fusion Equation, your power will be enough to shake Artosh."
"Wait for me to ask my Lord for instructions. I'll respond to your trade after obtaining the Lord's permission."
Jibril said as she flew toward the Main Hall where Artosh was located.
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