In DxD Starting with Sign-Ing in as the Red Dragon

There was no turbulence.

Soon, Chiba Akira's information was successfully recorded.

From today onwards, he could also call himself "King."

Just thinking about how his strength as a lower demon could qualify him to be a "King" made Akira want to laugh.

This is what demons are about: bloodlines above all, power above all, and interests above all.

....

Akira is a transmigrator.

Over a decade ago, he crossed into this world.

However, his crossing was quite ordinary; he had no special abilities or talents.

What he had was just a trace of succubus bloodline, a trace of Leviathan bloodline, and a companion Agumon.

Even so, that trace was still Leviathan's bloodline, which drew the attention of the underworld.

There was no choice.

The current Four Great Demon Kings needed a political benchmark.

...

The current Four Great Demon Kings are not the original Four Great Demon Kings.

After the original Four Great Demon Kings died in battle, the bloodline heirs of the original demon kings continued to rule the demon race.

These individuals who inherited the bloodlines of the original demon kings are now referred to as—Old Demon Kings.

After the war between the three major factions ended, a rift emerged within the demons.

The result of this rift was—demon civil war.

The current Four Great Demon Kings won the demon civil war and became the "New Demon Kings."

Those demons who inherited the bloodlines of the original demon kings were demoted to "Old Demon Kings."

The Old Demon Kings and their factions were unwilling to accept the changes from the underworld and refused to submit to the New Demon Kings. Some chose to hide, while others chose to flee.

As for Akira, he was said to be one of those little Karami who didn't escape and was found instead.

....

Because the New Demon Kings needed political claims,

Akira, this little Karami, transformed into the "heir of Leviathan's bloodline," and even gained a beautiful and powerful fiancée.

The current Demon King Lucifer married "Grayfia Lucifuge," the heir of the family that originally served Old Demon King Lucifer, proving his legitimacy to bear the name "Lucifer."

Meanwhile, the current Demon King Leviathan married the heir of Leviathan's bloodline... which is Akira.

That's right.

Akira's fiancée is one of the current Four Great Demon Kings in the underworld—Serafall Leviathan!

If nothing unexpected happens, Akira will become Serafall Leviathan's husband after coming of age.

However,

Unexpectedly, three years ago, news came from the underworld that his fiancée had changed to none other than—Sona Sitri, the sister of the current Leviathan Demon King.

Akira knew very well why such a change occurred.

Because... he was merely a speck of dust in this era, a tool used by the New Demon Kings to maintain stability and showcase their authority.

As times progress, his value is declining.

He must do something before his value completely disappears.

....

To avoid ending up with a tragic conclusion in this story filled with overpowered tasks, Akira has been making multiple preparations:

Putting all his effort into learning and practicing chess knowledge related to rating games.

Using resources obtained from his true demon king privileges to purchase monster corpses and essence blood to help Agumon grow stronger quickly.

Searching for powerful artifacts and divine tools from the original plot, striving to find adaptable ones to implant onto himself.

Establishing connections with certain plot characters using his innate abilities and prophetic powers, such as Azazel, Bael, White Dragon Emperor, Lavinia, Griselda, Serafall, Rebell...

Snatching certain plot characters that can be obtained without risk, such as Gasper, Irina, and Asia.

At this point, Akira's plans have been progressing smoothly.

It's estimated that in another three or four months, Agumon will evolve into Greymon.

Therefore, Akira doesn't want to be annulled so soon.

An annulment would mean his value would decline again.

An annulment would mean that resources obtained in the future would further decrease.

Even for the sake of getting more resources for free, Akira doesn't want to be simply annulled like that.

....

"By the way, Akira-kun, besides these two matters, I also want to make a deal with you."

Has Rias finally gotten to the real topic this time?

"A deal? What kind of deal?"

Akira couldn't think of anything he could trade with Rias for.

Could it be... she already knows he has obtained "the Red Dragon Emperor's gauntlet"?

....

Under Akira's gaze, Rias put down her teacup and smiled gently.

"Akira-kun, tell me, would five years' worth of monster resources convince you to temporarily act as my fiancé?"

Akira raised an eyebrow and thought for a few seconds before replying: "Rias, you should know that I have a fiancée. Even if you want me as a shield, those in the underworld will definitely not recognize it."

Upon hearing this, Rias slightly pursed her red lips and smiled lightly.

"That's right; Akira-kun is Sona's fiancé. So even if I say we are mutually in love, it wouldn't be recognized by those in the underworld."

"However, there are always exceptions."

"....."

"Rias, are you trying to say....."

Akira narrowed his eyes.

"Akira-kun should understand what I mean. That's right; Sona is currently thinking about how to annul her engagement with you~"

"I see. So what are your thoughts on this matter?"

Akira took a sip of tea; he had already anticipated this situation.

"My thought is for you and me to coordinate our statements and publicly say that we are mutually in love."

"If that's the case, I'll have a reason to deflect my brother and those old fossils from the underworld."

"When I graduate from university, we can part ways peacefully."

"At that time, I will gain my desired freedom and have more power to resist against the underworld. And Akira-kun can also obtain resources from me."

Rias's idea is quite good.

Or rather, it aligns well with Akira's thoughts.

Akira already felt that his engagement with Sona wouldn't last long; he planned on gathering resources for Agumon's evolution in those final years anyway.

Now it's great; a five-year guaranteed contract is right in front of him—what more could he ask for?

"Rias, can you pay it all at once?"

"For five years it might not be possible; however for one year it can be done," Rias replied after some thought.

"Alright then; I agree to this deal."

"Good! Then Akira-kun, from now on we are partners. Let's have a pleasant cooperation."

Rias smiled slightly and extended her hand proactively.

Their hands clasped in mid-air; after releasing each other's hands they exchanged smiles once more.

Plan successful.