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

The time for practical combat had arrived. Sigvira led Akira to a specially protected training ground, enclosed by a barrier.

"Akira-kun, take this practical training seriously," she instructed.

"Real combat is different from raw data. There are qualities that can't be measured in numbers—things like strategy, reflexes, battle awareness, and even sheer willpower."

"A high score in this test will raise your standing in the Underworld."

Sigvira wasn't exaggerating.

Both the written and combat data from this test would be recorded in the grand wargame simulation system.

Being part of that system meant high-ranking devils playing wargames could select candidates based on their performance.

If Akira proved himself to be a strong and reliable piece on the board, his reputation in the Underworld would soar.

"Akira-kun, your opponent in this test is a pure-blooded devil from the Astaroth Clan—Diodora Astaroth."

"His abilities are fairly balanced among pureblood devils."

"Good luck."

With that, Sigvira vanished into the teleportation circle, leaving only Akira and Diodora behind.

Seeing that they were alone, Diodora smirked.

"Akira Leviathan..."

"I've already looked into you!"

"Without your contracted beast, you don't even deserve to stand before me!"

Akira now understood why Diodora was acting so cocky—he was counting on the fact that the ability test prohibited the use of contracted beasts.

"I see…"

"So, you're afraid of Agumon?"

"Hmph! A low-class beast that relies solely on brute strength. Pathetic."

"As long as I'm prepared, it won't even get close to me!"

Diodora scoffed, acting tough.

Akira shook his head.

Diodora was the lowest tier of villains—the kind destined to be cannon fodder.

A true top-tier villain...

Needed elegance.

Needed strength.

And above all, needed the ability to manipulate others with reason.

At that moment, a notification rang in Akira's mind.

[Ding!]

[Congratulations! You have triggered a Sign-In Event!]

[Sign-In Grade: Purple → Silver]

[Sign-In Type: Multi-Stage Event]

[Event: Stealing the Fiancée]

[Summary: Scum like him has no right to boast in front of a true villain. A proper villain must completely destroy their enemy.]

[As everyone knows, the best way to ruin a man is to take what he values most.]

[The Saint was just a fleeting interest to Diodora, but his true weakness lies with his fiancée.]

[In the original timeline, after acquiring the 'Serpent' and rising to head of the Astaroth family, Diodora annulled his engagement, freeing himself from marrying into the Agares family.]

[But right now, he still needs to enter the Agares family as a political spouse.]

[Break off his engagement—then take what's his.]

[Or better yet, steal her before he even gets the chance to annul it himself.]

[Either way, it will utterly break him.]

[Mission: Stage 1 (Purple) – Break Diodora's engagement with Sigvira Agares.]

[Stage 2 (Silver) – Form a marriage contract with Sigvira Agares.]

[Stage 3 (Silver) – Make Sigvira Agares your servant… or claim her body and soul.]

[Stages can be completed in any order.]

"Damn… I almost feel bad for the guy."

"Not only will he lose the Saint, but even his fiancée is getting stolen..."

Akira shot a pitying glance at Diodora.

"Let's get started."

"I'll even let you make the first move. Try not to disappoint me, you weakling who only advanced by leeching off magic beasts."

Diodora crossed his arms and confidently stood in the center of the field.

Akira sighed, shaking off the last traces of pity.

Then, without hesitation, he raised his left hand.

[Boost!]

The Boosted Gear, the gauntlet of the Red Dragon Emperor, materialized!

BOOM!

For the first time, Akira was going all out, fully unleashing his Leviathan bloodline in battle.

His body had undergone a complete transformation!

With speed far beyond Diodora's ability to react, Akira appeared right in front of him!

At the same moment his fist collided, a powerful, enhanced magic shot erupted from his palm.

[Dragon-Shoot!]

BOOM!

Hit by an overwhelming force, Diodora was blasted across the battlefield.

"What was that…?"

Sigvira frowned.

That single attack had far surpassed the limits of a high-class devil.

"Ah, right… I almost forgot to mention," Rias chimed in belatedly.

"Actually, Akira-kun possesses a Sacred Gear—the Boosted Gear of the Red Dragon Emperor."

"Lady Rias," Sigvira glared, "next time, please report things like this before setting up the match."

At this point, the opponent she had chosen for Akira was completely useless.

"...Maybe not," Grayfia interjected, her eyes narrowing.

"The battle... seems to be changing."

She sensed it—chaos energy swirling around Diodora!

As the dust settled, Diodora stood back up, his body now surrounded by a terrifying aura of chaos.

High-Class Devil Peak.

Ultimate-Class Devil.

Mid-Tier Ultimate-Class Devil.

High-Tier Ultimate-Class Devil.

Ultimate-Class Devil Peak!

His power was skyrocketing at an absurd rate!

Even without attacking, the sheer pressure of his magic cracked the ground beneath him!

The fusion of chaos energy with his devil powers had shattered his previous limits!

[Name: Diodora Astaroth (♂)]

[Level: 144 → 194 (High-Class Devil Peak → Ultimate-Class Devil Peak)]

[Stats Evaluation]

(Compared to others at his level.)

Strength: C → CSpeed: B- → B-Magic: B → ADurability: B- → B-Martial/Technique Proficiency: C+ → C+ (Slightly above average for a pureblood devil.)Sacred Gear/Bloodline Ability: B- → B- (Decent talent, but poorly developed.)Overall Rank: B-Tier High-Class Devil → B-Tier Ultimate-Class Devil.

[Summary: A complete weakling who temporarily reached Ultimate-Class thanks to Ophis' "Serpent." Without it, he's just trash.]

Diodora didn't know exactly when he activated Ophis' power.

He only knew one thing—

"I'm going to crush you!"

"Die!!!"

"HAAAAAH!!!"

Diodora raised his hands, gathering an immense magic blast.

Watching him, Akira grinned.

Of course, he knew exactly what had happened.

Because…

He had triggered Diodora's "Serpent" himself.

As Diodora screamed, gathering his attack, Akira calmly raised his left hand.

Though Forbidden Forms became common in later arcs, at this point in the story—they were absolute.

Crimson draconic energy surged, emerald gems glowing with blinding brilliance!

[Welsh Dragon Balance Breaker!]

[Forbidden Move – Boosted Gear Scale Mail!]

Akira's body was instantly clad in the crimson armor of the Red Dragon Emperor!

A massive golden flame formed before him—

[Boost! Boost! Boost! Boost! Boost!!!!]

[SUPER FLAME!]

"Data readings are reaching Maou-class levels…!"

Sigvira's crimson eyes burned with excitement.

This…

This was the ultimate mecha armor she had always dreamed of!