I Reincarnated as a Mob Villain Prince Who Dies Before the Game Starts ~ In Order to Be Happy with My Favorite Heroine's Younger Sister, I Overcame My Weakest Magic [Dark Blade] with Excessive Effort, and It Became the Strongest Broken Power ~ - Chapter 3: The Mob Prince Protects His Sister from the Demon

Chapter 3: The Mob Prince Protects His Sister from the Demon

──And then, in the blink of an eye, four years passed, and I turned five.

In these four years, I continuously used my Dark Edge without taking a single break.

“Look, Dia, it’s scary, the Demon King!”

“Ah, big brother, so cool!”

I was playing pretend with my four-year-old sister, Diana, pretending to be the Demon King.

I created two blades of Dark Edge from my forehead, like horns, and stood proudly like a villain.

This was because the Demon Kings in the stories my mother read to me always had horns.

By now, I could generate Dark Edge not only from my palms, but also from other parts of my body.

With this, I could keep using Dark Edge while playing with Diana.

Diana clapped her hands joyfully.

Alright, it worked! She liked it!

Mother, Luna, had been urgently called by the Emperor early in the morning, so she wasn’t around.

In that case, I had to make sure to take care of Diana.

“The Demon King kidnaps princesses, you know. I’m going to catch you, Diana!”

“Ah! Big brother, I’m running away!”

We started playing tag in the room, which was way too big for children.

As always, no one else came to this prison tower except for Mother.

The lack of interaction with others in this environment wasn’t great for raising children.

So, every day, I made sure to play with Diana until she was satisfied, so she wouldn’t feel lonely.

Fortunately, we had a lot of picture books and toys here.

“I got you! From now on, you belong to me, the Demon King!”

“Hee! I’m happy, big brother! I’ll be yours! I’ll marry you!”

Little Diana blushed and returned my hug when I embraced her.

Diana had declared that she wanted to marry me in the future.

What is this? This adorable little creature…
My sister is just too cute…!

It’s hard to believe that this Diana will one day become a Demon King who brings fear and destruction to the world.

I guess it’s all due to the terrible environment she’s been raised in.

If I protect her and shower her with love, I’m sure a future where Diana falls into darkness and becomes the Demon King will never come.

“Alright, now it’s your turn to be the Demon King, Diana!”

“Okay, big brother! I’m going to catch you! Kneel before the Demon King, Diana!”

Diana took the role of the Demon King and chased after me.

Diana had somehow learned the Demon King’s speech. She’s just four years old, but she’s amazing. My sister is a genius.

“Wow, that sounds just like the Demon King! But, Diana, you can’t become a Demon King in the future. If you become a bad Demon King, I won’t marry you!”

“What?! I don’t want that!”

Diana puffed out her cheeks and stamped her little feet.

“Then I won’t be the Demon King anymore!”

Wow, she said something nice!

“No, no, that’s for when you’re older. For now, I want you to chase me!”

“Yay! Alright!”

I savored the happiness of my unchanging daily life with Diana.

But, in the next moment…

It suddenly happened.

A rush of intense heat surged from deep within my body.

“Ahh!?!”

I instinctively crouched down on the spot.

This was a rare magic power overload. I had been feeling lately that my magical power was increasing, but this time, it was very intense.

“Big brother!?”

“Diana, stay away! It’s dangerous!”

I held my hand out to stop Diana, who had rushed towards me.

“Dark Edge!”

Then, I generated a massive Dark Edge that reached all the way to the ceiling. This was the result of my four years of training.

It wasn’t something in the game, but as I accumulated mastery, I became able to change the size and shape of Dark Edge freely.

The massive Dark Edge consumed more magic power. I thought this would calm down the magic power overload quickly, but…

“No way!?”

Magical energy surged out at a speed that far exceeded the amount I was consuming.

What is this? Could it be that I’m really going to die now?

“Mother! Big brother is in trouble!”

Diana shouted towards the door, but there was no answer. Mother hadn’t come back yet.

In that case, I had to handle this on my own.

“I’ll create an even bigger Dark Edge and exhaust all my magic power!”

I enlarged the Dark Edge even more, making it reach the ceiling.

Then, there was a huge explosive sound!

“What’s that!?”

A large magic circle appeared on the ceiling and repelled my Dark Edge.

The shock from this caused my Dark Edge to disappear.

…Wait, I made a mistake.

This was a prison, meant to keep Mother trapped here.

If I tried to destroy the prison with magic, a barrier would be activated to stop it.

“Attempt to destroy the prison detected. The caster will be suppressed.”

An emotionless voice echoed, and the space near the ceiling distorted.

This was the summoning magic effect I had seen many times in the game.

With a roar, a massive demon-like monster with black wings appeared from the distortion.

“Groooowwww!”

“Ahhhhhh!?”

Diana collapsed in fear.

This was a Summon Trap. It was a magical trap that summoned a monster to intercept intruders, like those trying to break into a treasure vault.

And the monster summoned was an A-rank level creature──an upper-class demon, the Archdemon.

My knees trembled involuntarily.

They were prepared for this…

It seemed like Emperor Alvais had no intention of letting Mother escape from here.

“So, you’re the one who tried to destroy this prison and abduct the Dark Elf princess?”

The Archdemon stared at me with eyes like glowing embers. Its massive body weighed down the floor, causing cracks to form.

“A child like you? Well, whatever. It was a contract to devour anyone who’s foolish enough to break in! A young child is the perfect sacrifice.”

The Archdemon licked its lips, looking down at us.

Could it be…?

“Wait. If you try to lay a hand on my sister, I won’t hold back!”

I summoned Dark Edge again and braced myself.

My heart shrank with fear, but if this demon was summoned because of me, then I would protect Diana with my life.

“Big brother!?”

“Diana, hide behind me!”

I stepped forward to shield my sister.

“Dark Edge? Are you going to resist with such low-level dark magic?”

The Archdemon raised its hand, and countless fireballs appeared, rushing toward us.

“I’ll roast you alive.”

“My Dark Edge is not just any ordinary Dark Edge!”

I enlarged the Dark Edge and shielded Diana with it.

The fireballs exploded on the Dark Edge, creating holes, but the magic power quickly repaired them.

“It’s useless no matter how much you attack! I have the magic power to back it up!”

The attacks were intense, but I was managing to hold up.

If the Archdemon was part of a system to stop intruders from freeing Mother, then soldiers would likely be arriving soon.

If I could stall for time, I could protect Diana even if I couldn’t defeat this demon.

“What…?! Interesting! Then I’ll increase the magic power little by little. Let’s see how long you can last!”

The Archdemon kept bombarding us with fireballs.

And the power of the fireballs was growing stronger.

Is it playing with us?

Damn it! If this goes on, we’ll be overwhelmed.

“Big brother!?”

Diana called out with a worried voice.

But I promised Mother I would protect Diana.

If there’s a magic power overload, it’s actually in my favor. I’ll squeeze every last bit of magic power out of my body to fight back.

A bigger, harder, thicker Dark Edge that goes beyond a sword’s realm…!

“Here, this ends now!”

The Archdemon created an even larger fireball and hurled it at us.

Boom!!!

The entire prison tower shook with the explosion.

But the flames and shockwaves didn’t reach us.

“Impossible…!? What…what is that?”

I had transformed the Dark Edge into a thick, massive shield. It was as solid as a castle wall.

“I call it Dark Edge Wall!”

“How can my most powerful magic not work!?”

The Archdemon trembled in shock.