Here you go guys, some backstories about Yuuki.
After leaving the Ingracia Kingdom’s royal capital, Yuuki’s group was leisurely traveling along the Great Kanat Mountain Range towards the East Empire.
The safer route to the empire’s territory passes through the Dwarf Kingdom and would reveal their location to Rimuru and co.
Since Yuuki had never travelled to the east before, he couldn’t transfer there with magic.
「Well now, mountain climbing can be fun every once in a while.」
Yuuki spoke in a carefree tone while he tore apart a low-class dragon that had come to attack them.
Kagari responded by shrugging her shoulders while Yuuki’s supervisors, who he’d formerly dispatched to several countries, and were his trusted retainers remained silent, observing their surroundings quietly.
Yuuki, bored by their response, looked up at the summit.
The route Yuuki’s group was following was one that passed above the Dwarf Kingdom and was rarely traversed.
The wild dragons that inhabited the area were a high-class life-form that could understand human speech if it became a higher species.
They were uninvited guests on these mountains so it would become troublesome if they were discovered by a King Class dragon.
Aware of this, Yuuki and co. advanced carefully.
Compared to Yuuki who seemed to be having fun, shadows of fatigue could be seen in his subordinates.
It wasn’t surprising since they had been attacked by lower-class dragons once every hour. Up to five dragons have attacked at once. If they went through the safer route commonly used by merchants, they wouldn’t be attacked like this and dragons would rarely appear.
The route that Yuuki and co. were traversing wasn’t a route approved by the Dragon King.
Maybe because of that, they were extremely cautious. Yuuki had chosen this route without hesitation.
At that time,
「Oh? A call from Leon. Recently, he was mad and said that he would cancel our deal, does he still have complaints?」
While saying that happily, he took out a necklace with a small crystal from his breast pocket and charged it with magic power.
And somehow the conversation with Leon occurred,
「It seems like Leon will come here. Since it’ll take him approximately an hour to get here, shall we take a break and wait for him?」
He informed Kagari and the others before he immediately sat down on a sturdy and comfortable rock.
「Leon...? The Demon Lord, Leon? Will it be alright?」
「Is there a possibility that it's the Demon Lord Ruminas and co?」
「Is it fine for our location to be given that easily?」
So his subordinates and Kagari questioned.
「Eh, it should be fine. After all, he was a regular client.
Besides... even if the Demon Lords unite and come along, there’s still Chloe.」
He replied optimistically.
Kagari and the subordinates realized that it was useless to even say anything now.
And so, after an hour, they would face Leon.
A meteor emitting golden lights appeared in the sky.
A meteor emitting golden lights appeared in the sky.
Though it was daytime, the golden lights were clearly visible.
It might have been guided by a detection series magic as it flew straight to Yuuki and co. without wavering.
It was the Demon Lord Leon and his Knight subordinates.
Leon was wearing a golden armor, and his colorful knights wore silver, black, red, and blue.
「Did I keep you waiting?」
Said Leon as soon as he landed.
「No, it was a nice rest. By the way, it seems to be urgent business, what is it?」
Yuuki answered with a radiant smile.
「I heard you were lying to me and could not be trusted.* I came to find out whether or not it was true.」
Yuuki answered Leon’s question with a smile.
Invisible sparks flew between them, the tension around them instantly growing.
「You, did you think you could use such a lie against me, a Demon Lord?」
「Ahahaha. As expected, was my lie exposed?
Even so, if you wanted to realize it, you should have realized it sooner. You’re already too late, you know?」
With those words as a catalyst, the rock Yuuki sat on instantly melted into lava. It was the effect of a Scorching Magic attack.
Yuuki left the spot quickly. The opponent’s reaction to his response was as expected.
In the middle of the conversation, Yuuki hadn’t neglected to analyze Leon and his subordinates’ strength. The problem was whether or not Leon would be attacking by himself.
Were there reinforcements from the other Demon Lords? Was Leon just a decoy? Or was he alone?
Depending on the answer, it would be necessary for Yuuki to switch strategies. Yuuki had expected this development since he’d received the call.
Leon, as a high-ranking Demon Lord, he was not an opponent whose strength he could make light of.
If that Demon Lord decided to join ranks with the other Demon Lords in a united front, it would even be difficult for Chloe to handle them by herself.
Therefore, he chose this place.
「Hey, hey, it’s not gentle to attack suddenly.
Your important Girl is over here, do you know the word Hostage?」
He called out to Leon in an attempt to agitate him, but…
「Don’t worry, if you die, she’ll be released right?
What I requested was a girl, around eight year old with black hair, named Chloe Aubert.
She’s already grown up and is standing right there!」
Leon ignored Yuuki and denied his words strongly.
Hearing Leon’s words, the girl with black hair, Chloe, opened her eyes.
「Eh, Leon-Oniichan? You’re alive?」
She murmured lightly in surprise with a voice full of nostalgia.
「Tch, it can’t be helped if it was exposed.
I kept quiet about having kept Chloe-chan as a trump card against the Demon Lord, however…
Somehow, for a certain period of time, I had forgotten about it. When I remembered, she had already grown up as a Hero.」
Yuuki mocked Leon. Furthermore, he continued,
「Even so, it can’t be helped right? You are a wicked Demon Lord.
To exterminate you is the Hero’s task, right?
If you think about it, it is a pleasant miscalculation that Chloe grew into a Hero.」
So Yuuki declared.
Without letting his heart be disturbed by Yuuki’s response, Leon said…
「Fu, is that the only thing you want to say? Then you shall die satisfied!」
Leon started attacking Yuuki with a high output magic.
And so, the battle between Leon and Yuuki began.
The heat wave from the magic closing in on Yuuki raged to violently burn his body.
Yuuki looked at the heat wave with a refreshed expression, and a small grin floated on his face.
Mostly, it was just as planned.
But it wasn’t going exactly as he’d wanted.
He had considered the possibility of an attack from several Demon Lords, but judging from the current situation, it was only Leon.
Hypothetically, in case the three Demon Lords, Rimuru, Ruminas, and Leon came to attack him together, the probability of winning would be small, even if he let Chloe participate in the battle.
But it was an assumption that Rimuru and Ruminas would unite and attack him. It was unexpected that Leon would participate in the battle, but since Chloe was involved, it was certain he would have become hostile sooner or later.
If he thought about it, it was unexpected that the girl, who Leon had entrusted to him, had become a Hero.
Ever since he’d learned of it, he had always been aiming for an opportunity to snatch away the “Sleeping Hero” enshrined by Ruminas.
This was for the sake of obtaining a trump card against Ruminas.
Rimuru was a suspicious reincarnated person from the same country as him and had shown an uncertain growth. He had planned to quickly get rid of this irregularity.
But it ended in failure, Rimuru became a Demon Lord.
Since it became like this, he had planned on making the children his trump card. He was going to gather trump cards against each Demon Lord so that he could take care of them with ease if he had to fight with them.
His ultimate target was the subjugation of Demon Lord Guy Crimson.
He was going to make as many Demon Lords abide his orders as possible in order to subjugate that absolutely strong person.
Working vigilantly and cunningly, the Demon Lord didn’t stand a chance at all. Millim was also an absolutely strong person, but she seemed easy to trick and couldn’t be labeled as a threat.
In other words, as long as he could defeat the Demon Lord Guy Crimson he would consider what to do afterwards, but......
In reality, such an unexpected thing had occurred, it was interesting!
Yuuki felt a pleasant, exhilarating feeling in his heart when the plan didn’t go as he’d expected.
Kagurazaka Yuuki was a genius.
When he was still in the former world, he had harbored dangerous dreams of destroying the boring everyday life. It was just that, in the former world, he hadn’t held a fascination for the world’s destruction.
Earning money wasn’t a problem for him either, if he wished for it, he could obtain it, but for him, there was already nothing he really wanted.
When Yuuki had just become an elementary school student, his parents were killed in an accident. His parents hadn’t made a mistake, they collided head-on with a truck whose driver had fallen asleep at the wheel, and died instantly.
Only Yuuki who was sleeping in the rear seat survived.
Yuuki had thought that it was unreasonable.
The world was too unreasonable, and he was too powerless.
Thinking about revenge against such an unreasonable world had become amusing. But he quickly grew tired of that.
He was a genius that could accomplish anything that he wanted.
If he seriously wished for it, it might really have been possible to turn the destruction of the world into reality.
It’s uninteresting. This world is really boring.
He didn’t lie about his true feelings.
But, it could be said that his rampage was suppressed because of that.
While it was a good fortune for Yuuki to have crossed to this world, it had become a misfortune for others.
Kagurazaka Yuuki crossed worlds and acquired the power that his soul had wished for. He who wanted all, in reality wanted nothing at all.
Therefore he obtained the “power” itself.
The name for it is, ――Unique Skill『Creator』――
The power was a miscalculation for Kazaream who had summoned Yuuki.
No, in the first place, that the summoned was Yuuki meant that it was a failure (fate) for Kazaream.
Kazaream who was a “Drifting Soul” took several hundred years to prepare for his own revival, to increase the covenant with the summoned target.
Failure was not allowed in the ceremony, but just in case, he engraved a curse crest implementing his control ability and did the summoning.
The summoned target couldn’t keep its consciousness and Kazaream had planned to destroy its spirit and kill it. Afterwards he was going to snatch the power of the soul and take over the body in order to revive. The covenant that should have been perfect was easily broken by Yuuki, the summoned target. With the power of the soul that Yuuki had obtained, the curse mark was reflected through reverse analysis.
With his own skill overturned, Kazaream easily surrendered to Yuuki.
And so Yuuki went to another world.
In this world, powerful enemies existed; it was a world without boredom.
Yuuki rejoiced, he knew the meaning of his own existence in this world.
Let’s bring destruction to this world. If you want to stop me, then show me if you can!
It was Yuuki’s code of conduct.
A warped retribution against such unreasonable world.
Therefore Yuuki doesn’t get impatient. It doesn’t even matter if he fails.
In case he succeeds, then the world will be destroyed and he may die in highest pleasure and joy.
Perhaps he would create a new world and become its god, but…Yuuki hasn’t thought that far ahead.
His desire is to challenge the world. It’s to fulfill his warped desire.
Yuuki understood the world’s structure with his genius.
First of all, he grasped the principle of summoning in the world and created the Unique Skill 『Summoner』.
After that, from Kazaream’s skill, he created the Unique Skill 『Ruler』.
He created the ability after spontaneously comprehending the structure and changing it so that he could use it.
After that, he would learn the skills he liked from the people he met and acquired a great number of abilities.
Fitting for his status of a genius, he didn’t need a lot of time to obtain overwhelming power.
He obtained the Unique Skill 『Plunderer』from Hinata. Her 『Mathematician』skill wasn’t necessary for him. The reason was that his thought speed was better. If it was in the former world, his impossibly quick calculation speed could have burnt his cerebral nerves, but that wasn’t an issue in this world.
The reason is that when he was summoned to this world, his entire physical constitution was renewed and changed his body into a type of spirit life-form.
Thus, Yuuki exceeded the limits of this world.
Thus, Yuuki exceeded the limits of this world.
Yuuki was convinced that his power would be equal to a Demon Lord in 10 years.
However, he couldn’t be careless.
Even is if he was certain of his power, when he noticed that his figure hadn’t changed at all, Yuuki had already noticed that his lifespan was no longer of concern.
It was unnecessary to get impatient. He would advance surely and carefully.
Yuuki pushed his plan forward as slowly as he personally wanted.
He may be able to defeat the Demon King, but he wasn’t certain.
Therefore, first of all he procured trump cards.
Against Leon was the girl Chloe.
Against Ruminas is the Sleeping Hero.
Against Rimuru are the Children.
However, the girl Chloe was the Sleeping Hero.
He also lost Hinata, who had been under his control. However it couldn’t be helped.
He made a contract with the Hero Chloe.
Against the Hero who had just awakened, he attempted to control her using all the power of his Unique Skill『Ruler』.
Yuuki concentrated all his energy into that one skill. Even though he did that, it was an existence impossible to completely control.
He stopped all his plans and decided to control the Hero.
「Soon, Hinata will come to rescue the children.
At that time I will fight Hinata. Therefore, I want you not to interrupt.」
It was a mistake to bet against the Hero Chloe who said could predict the future.
According to Yuuki’s prediction, the one who would come was Rimuru who had become a demon Lord.
When Rimuru came, he was going to let Chloe fight him and at that time he intended to gain control over him.
But, Yuuki realized the optimism of his own thought as the bet resulted in failure.
The Hero Chloe, was likely an existence outside of the World’s Law.
Even with his ruling ability, she was an existence that couldn’t be completely dominated. She was an existence he couldn’t fathom, even with analysis.
However, fortunately, he succeeded in engraving the “Curse Seal” on her.
Even when he used all of his “soul’s power” it was still impossible to control her.
Even so, he could command her for three orders. Still, this girl had immeasurable potential.
But the plan failed completely.
Even so, obtaining this Hero still had some potential significance.
Above all else......
It was a mess; it had become very interesting!
The Demon Lord Leon was before him.
It was certain that this man was superior to him.
Even with Yuuki’s ability, he was an opponent that couldn’t be read.
With Yuuki’s ability, he could analyze a normal Unique Skill right away.
If he couldn’t read it, then the opponent’s rank was higher than Unique Skill.
According to Kazaream, she said the attack was a current of light that destroyed all.
It reminded him of the “Disintegration” that Hinata used.
It was the strongest Holy magic.
But Leon didn’t need to chant; it also seemed that he could activate it instantly and without limit.
Just thinking about it made him tremble with excitement.
《Confirmed. Acquisition of Ultimate Skill『Greedy King Mammon』・・・Succeeded》
The Voice of the World echoed.
On this day, at this moment, in this place,
The worst Devil was born.
 Truck-san ga kita!
 Can also mean Unjust
 魂の力 Tamashii no chikara Power of the Soul/Soul power/Spirit power.
 本質 Honshitsu, can also mean substance, nature, and reality.
 創造者 Souzousha, so his Unique Skill make him technically a god.
 漂う精神 Tadayou Seishin
 召喚者 Shoukansha
 支配者 Shihaisha
 He uses the original skill as the base and modifies it to his use.
 強奪者 Goudatsusha
 強欲之王(マモン) Gouyoku no Ou (Mamon). King of Greed/Ruler of Avarice etc.
Next chapter is about the fight between Yuuki and Leon (Mammon vs Metatron)!