77 Control is oftentimes more important than pure power

After some banter and a brief rest, they finally arrived at the crux of the matter.

"So...."

Rias began, trailing off and her gaze sweeping over herself.

Her beloved school uniform was torn in many places, proving the ferocity of their battle. And despite the silver-haired body healing the redhead, the sweat her body exuded didn't disappear

Instead, it caused the torn fabric to cling to her figure- with such a ruined outfit glued to herself, it is safe to say that her body was on full display, and all her assets were proudly shown off

Of course, the busty devil wasn't embarrassed by this, she even put her hand on her hips, further emphasizing her developed physique

Adam was observing her, his eyes attracted by all of her features as he was mentally undres- Ahem- staring at her with a focused expression to make sure no injuries escaped his healing previously

... Just because the reincarnator can beat a beautiful girl mercilessly doesn't mean that he isn't attracted to her, on the contrary, it means that he has affection for her because he wants the girl to get stronger with his guidance

"Are we going to train in this condition...?"

The redhead devil spoke up, continuing her previous line of thought as her eyes shifted towards the tear she inflicted on the silver-haired boy's forearm

"No" he replied, shaking his head in denial "Don't worry, I have a solution for this"

Finishing his sentence, Adam approached her, his coat slightly fluttering with his movements

Standing in front of Rias and looking at her straight in the eyes, the silver-haired boy reached out, placing his hand on her chest

"Eh...?!"

The busty devil's body jumped slightly, her eyes widening and snapping at him in disbelief

"What are you-?!"

Opening her mouth to question him, she was interrupted as something magical happened

In front of the hand that was placed on her chest, an intricate magic circle appeared.

The circle contained different runes with various colors- within it, there was a hexagram that had different triangles that glowed with a magical light

... It was unlike those that were used in the redhead's world- in fact, it was completely different from what the devils in her world used

With a flicker of light, her torn uniform was enveloped in a golden mist, transforming before her eyes.

The glow subsiding, Rias looked with widened eyes. Her uniform had completely recovered to pristine condition. The previous tears were nowhere to be seen, as if the previous battle never took place

Adam receded his hand from her chest. Instead, he raised in front of his chest, the same phenomenon unfolding as the same tear she caused to his outfit disappeared

"How?"

The red-haired devil asked him, intrigued at what just occurred.

Although something like this isn't that amazing when compared to all the supernatural wonders that are present in her world, it is still something cool

"Alchemy"

Adam replied curtly, a simple word being his short answer as the magic circle(?) dissipated

"...."

Something clicked in her head after his reply. Memories of something she had watched quite some time ago appeared in her mind

"Full metal alchemist?"

"How did you know?"

"Hmph" Rias snorted, her arms under her considerable bust as she had an expression of pride "I'm a certified otaku, do you think I wouldn't recognize that magic circle?"

Adam just raised an eyebrow at her, a thoughtful light crossing his eyes for a brief moment before it disappeared

"By the way..." The redhead tilted her head "Wasn't there something about equivalent exchange or something? How did you fix my uniform without materials?"

Full Metal Alchemist, an anime about alchemy(... Obviously). She could vaguely remember terms like equivalent exchange- something that allowed transmutation- which also needed a material of equal value to be exchanged for it to be successful

"Mnm"

The silver-haired boy nodded, lazily crossing his hands in front of his chest

"We are not in the Full Metal Alchemist world" He said, shaking his head lightly "And I don't even have a Gate of Truth, so those rules don't apply to me"

...

In fact, Adam had already read the whole book back in the honkai world.

With his increased mental strength, digesting knowledge manually was far easier- and it was also a subject which he was interested in, so that ease intensified

At first, he was quite confused about what he was supposed to do. After all, a 'a gate of truth' is what makes alchemy in the FMA world possible, without it, how would he be able to do the same?

But actually, it wasn't that complicated. With the help of [Great Sage], he managed to find a way to replicate the method of Alchemy, but he needed a good energy source to do so

Honkai energy would be ideal, as it was already proven to work in constructing objects with the power of the Herscher of Reason.

Although he didn't have that ability, transmuting materials with honkai energy isn't difficult

As some people say, honkai is omnipotent!

.... Still though, in the future, he will have [Great sage] make progress by analyzing the Relic of Creation and Ambrosius' ability to create 'anything', so this problem won't haunt him for long.

He would probably be able to create whatever he wants on his own, which while limited, will make it shockingly easier to modify already existing stuff with transmutation and Alchemy in general

"By the way" He spoke up "Your uniform wasn't destroyed- it was just torn to pieces and scattered. Gathering all the pieces and putting them back together with energy isn't difficult"

Besides, energy can neither be destroyed nor created. That applies to objects too, while their form would change, they would still not be destroyed. Of course, it depends on your view of a 'destroyed object'

After all, reducing something to atoms or particles isn't really included in people's philosophy of 'The atoms that this object is made out of are still there, so the object isn't destroyed'

It is the same matter when an object transforms into energy. It loses its form and becomes energy, and that process is normally irreversible

... Maybe an exception to that rule would be erasing something from existence. He doesn't really know what to do in that case

"Besides...."

He spoke up again, the time passed in his thoughts being negligible due to [Thought Acceleration]

"Demonic power is quite malleable, so I can just supplement something with this energy to perform transmutation"

A smirk slowly emerged on his face, his expression a bit mocking

Such a malleable energy source... No wonder it can theoretically be transformed into the user's desired state with just imagination

... Which is exactly why his expression was a bit mocking.

Devils- despite having such a great and potential-filled energy source- are still not the strongest race, and they are still forced to resort to transforming other races into devils in order to repopulate their numbers

"Can you teach me?!"

Rias cupped her hands together in her chest, looking at him with pleading eyes as she didn't catch the hidden meaning behind his words

"Haha" Adam chuckled at her excitement "You need to control what you already have before you obtain new skills and abilities"

The silver-haired raised his hand and touched her head, the corners of his mouth curling up as a helpless light flashed in his eyes

"Okay?"

He looked at her seriously, his hand lightly petting her red hair

"Mhn" The busty devil nodded meekly, her eyes darting to the side, avoiding eye contact

Raising an eyebrow at her behavior, Adam retracted his hand

"Ahem"

He coughed, attracting her attention

"It's time for the actual training to start"

....

..

.

"Actually, training is a very simple matter"

Adam, his hands crossed behind his back, explained to Rias who was listening attentively

"Now, there are three things you should keep in mind from now on" The silver-haired boy raised his hand, raising three fingers "And that is power, energy, and control"

He explained in a calm and patient voice, capturing the redhead's full attention

"Power is self-explanatory..."

He shook his head "But think of it like this- If you made a fireball, and your brother also made a fireball with the same energy amount you used, which would be stronger?"

The busty devil rolled her eyes at him "My brother's, obviously"

"That's right" He nodded "Despite using the same energy amount, the fireball your brother created would be marginally stronger. Countless factors contribute to this phenomenon, but it shouldn't be your concern for now"

Rias nodded, expressing her understanding. Although she seemed a bit irked that he didn't explain it further, she trusted in his judgment

"As for energy...." Adam trailed of, a hint of golden flashing in his eyes "That is even more simple, it is simply the quantity and the quality of your energy source"

"Also, there are different types of energy, some excel in different areas... And others are simply superior in every way"

"But I believe you already have an idea about this, right?" He looked at her, already expecting her to have some knowledge in this field

"Ah...." The red-haired devil blinked owlishly, her eyes flashing with understanding "Are you talking about Touki, Senjutsu, Demonic power, Holy power, and divine power?"

As the little sister of the strongest devil, it would be shameful for her not to know about the different types of energy that exist in her own world.

After all, some of her peerage members can use a different types of energy, so she is obviously aware of them as they are quite relevant

The DxD verse is a supernatural world with a lot of variety. There exists gods, devils, angels, yokai, and even some other mythical beings- and with so many different creatures, there also exists different types of energy that the races of that verse utilize to achieve various purposes

"That's right" He smiled slightly, satisfied that she wasn't completely clueless "Except for the quantity and quality, there are also different types of energy that are simply better and more convenient to use"

"Think back to the strongest being in your world except dragons" He continued "If you were able to use your power of destruction with the divine energy of the gods as fuel, what do you think would happen?"

Rias' eyes lit up in realization, her mouth opening to enthusiastically reply to him

"I would be as strong as those gods in the top 10- Ouch!"

Her excited sentence was cut short by Adam, who flicked his finger at her forehead.

With his expression and the way he looked at her, he seemed like an older brother chastising his mischievous and foolish little sister

"Wrong" The silver-haired boy shook his head in disappointment "You would simply explode and die horribly, your body wouldn't be able to handle the strain of using divine energy"

After all, if everyone could handle a higher grade of energy, the higher beings of different worlds wouldn't be so few in number.

In Rias' case, using divine power would not only explode her body, but also destroy her soul

He didn't know what energy source the deities of her world used exactly... And although divine energy is different in every world, it still shares some similarities across the board, and even if it was somewhat different from what he thought, the redhead still wouldn't be able to contain it as she is too weak

"Hmmm....."

With a humming sound escaping her mouth, Rias pouted at him, her cheeks puffed up as she slightly glared at him

"Alright..." She said with annoyance "I was just excited, okay?! I didn't think of what it would do to my body!"

Adam rolled his eyes at her, temporarily ignoring her foolishness as he opened his mouth to continue

"Next is control" The silver-haired boy said with his hands behind his back "It is quite obvious, but it is the skill at which you handle your abilities and skills. It also refers to what level you have practiced or refined certain techniques"

"For example...."

Trailing off, Adam brought a hand to his front, raising his palm in the air as his eyes slightly glowed

An oppressive feeling arose in the atmosphere, a reddish-black ball of pure destruction manifesting from his palm.

His destruction-coated hand glowed in a similarly colored aura, the ball in his hands crackling slightly

But contrary to her expectations, the ball of destruction didn't explode on his face.

Under Rias' wide eyes, the magical shape of destruction stayed still, before compressing into a small but dense orb

Her mouth agape, she watched as the condensed orb of destruction changed shape slowly, transforming yet again as it changed into a thin but long needle-like shape

The silver-haired pointed to the sky, his palm wide open to allow the needle passage

FOOSH

The air rippled as the shape of destruction launched into the sky with intense speed, propelling itself to the clouds as it continued ascending to the sky without exploding or losing its shape

"Now that...." He trailed off, putting a hand on his hip as he looked at her with a condescending expression "... Is how you properly use your power of destruction"

"I-you-!?"

Was all Rias managed to stutter out, her eyes still widened as the dumbfounded expression still stayed on her face

"How-?!"

"It's not difficult"

Was his simple response as he interrupted her, a nonchalant smile being present on his face

The redhead opened her mouth, wanting to question him about 'How someone who got the power of destruction for just a day could use it better than her'

But she shopped herself, trying not to feel negative that someone who was unfamiliar with POD and demonic power just used it better than a high-class devil, one who was Lucifer's little sister no less!

...

..

.

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A/N:

I'm not a scientist. And I rarely pay attention to physics in school

So if I made any mistakes and assumed something wrongly, do correct me