The Substitution of the Shield Hero

To summarize Mister Demon's intel...

He was from the world that was currently intruding on my world- I mean, 'our' world.

Anyway, he was from the world that was connecting to ours in the waves.

Apparently, he was part of the Demon Dragon Nation, ruled by a Demon Dragon Emperor.

Said nation covered a whole continent and was held under the iron grip of said Demon Dragon Emperor.

Needless to say, I couldn't let myself be shown up like that.

And considering Mister Demon had apparently been mid-assassination attempt on Mein, according to my system messages...

Well.

I couldn't let that slide.

Mister Demon trembled in visceral fear when he saw the glowing blue portal connected to his world. "...You can... just do this? Open a portal even when the waves are not active...?"

Bahamut chuckled. "You chose quite poorly. But since you cooperated, you will live." He let out a sharp grin, revealing suddenly pointed teeth.

Huh.

Bahamut must have picked up some tricks while I wasn't looking...

Mister Demon gulped and quickly nodded. "I-I am grateful for the mercy, Oh Great Lord of Libertas..."

Bahamut nodded again and said, "You should be. Father usually processes his enemies and eyesores into resources. The last humans who crossed him became diamonds, fertilizer, and blades."

Mister Demon froze and turned to look at me.

I smiled and pulled out a handful of diamonds from my inventory. "Would you like to take a look?"

They were the processed remains from a few of the more degenerate nobles.

And while I hadn't been able to sense it before, after learning about the Spear's power-up method and how it harvested souls...

Well, I could clearly hear the agonized and desperate screams of souls stripped from the cycle of reincarnation.

And Mister Demon clearly could hear them too since he looked at me with existential dread. "...Y-Y-You are not a hero. Or a human. O-Or even a god... W-What sort of entity are you to handle the most sacral of essences with impunity...?!"

I grinned, just like Bahamut, and said, "Do you really want to know?"

"No, Great Lord! I fear not! I dare not!" Mister Demon started shaking on his feet and stiffly turned towards the portal. "Sh-Shall I lead the way?"

Bahamut smiled, idly twirling the golden hilt of his 'Ultimate Weapon.'

At the same time...

"Are we all going together then, Naofumi-dono?"

"I do believe that world will be shattered with our collective forces if we all enter, Master..."

...Lia and Sylvia glanced at me, double-checking.

I paused to think about that.

It sounded like fun.

Since that world had demons, and since the 'Demon Dragon Nation' sounded like a straight up Demon Continent from an old SNES JRPG, I really wanted to go and LARP as a proper Yuusha.

Buuut.

I sighed and said, "That's a good point. If Mein's already there, and since Mein took the initiative to start solving that place's problems, it would be rude of me to just barge in."

Even if she was still technically my servant on paper due to being grandfathered in and now technically a concubine (if Mirellia wasn't joking earlier), Mein was actively moving like a good person right now on her own volition.

Me stepping in would be crushing that volition of hers. So...

"Fine. I'll go kill a different demon dragon then."

Bahamut looked at me with glittering eyes. "Does that mean I get to have an adventure, Father?!"

"...Under adult supervision." I looked at Daji and said, "Would you kindly make sure the kids don't... I dunno, decide to conquer the world and declare themselves god emperor or something?"

Daji chuckled. "You mean like yourself, Naofumi?"

"No, because I haven't declared myself god emperor."

Yet.

Daji raised an eyebrow. "I sense a 'yet' there."

"No you don't. Now shoo." I waved my hand. "Go have fun or something on your isekai adventure."

Bahamut gave me a quick hug and said, "Best Father. Bye. I will do good."

After that, he sprinted towards the portal.

"Wait a minute!" I processed his words and said, "What do you mean 'DO' good?!"

Bahamut gave me a cheeky wink and dove through the portal, dragging Mister Demon along with him.

Lia giggled and immediately ran after him, probably to prevent damage control.

Sylvia sighed and followed.

Daji chuckled and then gave me a flirty wink before following after them. And when she did, I closed the portal.

That left just me, S'yne, Lucina, Morgan, Mirellia, Melty, and Filo.

Well, Rishia, Nina, and Mina too, but they were having fun fishing together since my daughters got bored of the talk.

Lucina looked at me with a curious look and said, "Naofumi... What did you mean when you said you were going to kill a 'different demon dragon?' Is there another one that you are aware of?"

Morgan's blue eyes flickered with excitement as he held Falchion. "Yes, Mister Naofumi! Is there more enemies to defeat?!"

"Kind of." I glanced at Mirellia. "Mind keeping a watch on my daughters with Rishia?"

Mirellia looked back at me with mirth clear on her face. "Should I be offended or flattered that you are entrusting me with your children? Especially since you so rudely turn down my advances..."

"Flattered because I'm including you."

Mirellia chuckled. "Very well... And I suppose it would be peaceful then. I have a feeling that this world will finally know some calm after you have departed from this plane of existence."

I raised an eyebrow. "That sounds kind of like you're saying you want me off this mortal coil..."

"Even if so, you are not particularly 'mortal' anymore, are you, Naofumi?"

"...Touche." I chuckled. Then I paused and said, "...Also, keep them away from Mom and Dad. Also Uncle Dante if he shows up."

"Of course."

Lucina kept looking at me, confused. "...Naofumi? You did not answer my question..."

"Hm? Wasn't it obvious?" I turned to look at her and said, "We're going to Ylisse. Your Ylisse."

Lucina's breath hitched.

Morgan's eyes flashed with fury, resolve, and yearning. "...Mother's homeland?"

"That's right. Unless you don't want to?"

Lucina stared at me.

I gave her a soft smile. "We can't change the past. But we can settle the present. Right?"

"...You are quite a cruel man. Aren't you?" Lucina's eyes watered a bit. But then she let out a shuddering breath and gave me a resolved look. "Very well. Show me then, Naofumi." She walked forward and gently held my hand. "...Prove to me that no matter what the future holds, I can cherish every moment."

I smiled and lightly squeezed her hand. "Of course, Lucina."

I felt a fierce side-eye from Mirellia.

Obviously, I ignored it.

Instead, I started walking forward and said, "Let's go, Morgan. Also, be careful. I'm not too sure how everything will adapt when we arrive."

"Understood, Mister Naofumi." Morgan nodded and then walked on the otherside of his mother, flanking her.

"Alright. Now, as for where Ylisse is..."

Portal Shield let me warp to any of my allies. It also let me warp them to me, but the key part here was the former function.

Now, I had never been to Ylisse. But I had proven that my abilities could include nations as 'allies.'

And so...

"I declare: the nation of Ylisse ruled by the last Exalt, Lucina D'Ylisse, daughter of Chrom, and one ravaged by the Fell Dragon Grima is my ally."

A tangible ripple spread. Like existence itself was listening in on me.

At the same time, I felt a gaze on me from dimensions away.

Draconic, malevolent... and amused?

"...Oh, you motherfucker."

Feeling that, I swept my left hand that was equipped with my Portal Shield and opened an azure portal. "We'll see if you're still laughing once I rip your fangs out to make blades. Let's go."

After that, I stepped through the portal with Lucina and Morgan.

===

S'yne watched as Naofumi left through the portal with Miss Lucina and Morgan. Then she turned towards Mirellia and said, "...I believe Mister Naofumi forgot about me..."

Mirellia chuckled and said, "Yes. He seems to have that habit... The women who fall in love with him are truly unfortunate."

S'yne tilted her head. "...Does that not include you?"

"Which is why it is unfortunate." Mirellia smiled.

S'yne sighed. "Still. To leave me be-"

Before S'yne could even finish her words, she vanished in a burst of blue light.

Mirellia blinked. And then she said, "Oh. Of course." She chuckled. "He could do that. Summon his allies to his side."

===

A world wreathed with tangible malice.

A once pristine palace shattered into rubble and ruins.

Masked undead shambling in every direction.

And above, floating in the bloody sky, there was a massive dragon that seemed to reach into space itself, looking down upon everything with multiple crimson eyes.

"...Ah." I looked up at the Fell Dragon Grima and slowly said, "Lucina. You didn't tell me that Grima was extraplanetary."

Lucina froze, staring at the massive dragon floating in the crimson skies. "...I was not aware. But... it HAS been at least five years since I have been to my Ylisse. More if we include the time I was with Father in the past."

"I see." I watched as Grima started charging a ridiculously overpowered energy attack. One that wasn't mana, but just raw *power.* "Well. I guess there's time to test something out."

I quickly summoned S'yne, who appeared in a burst of blue light.

"-hind without so much as a- Huh?" S'yne blinked in confusion. "Miss Mirellia- Wait, Mister Naofumi? What are you-"

"Sorry in advance."

"Sorry for what-?"

I pulled S'yne in and gave her a quick and chaste kiss.

"Mmph?!"

Lucina's eyes widened in surprise and confusion. "Naofumi? What are you-?"

Pure white light from S'yne's wings as they suddenly flapped, turning from small and violet butterfly-like wings to full angel wings that were a pure white. At the same time, the violet gem on her Vassal Sewing Kit shone an azure light, turning into a beautiful and resplendent indigo.

Then Grima's attack reached us.

Violet lightning crackling with enough power and heat to turn almost anything to ash.

But...

I laughed as I watched S'yne grab the lightning, immediately weaving it into threads.

...Conceptual weapons were bullshit as always.

*WHAT IS THIS SORCERY?!*

A booming and grating voice that seemed to echo from all around rumbled through the air.

Lucina instinctively trembled with fear before forcing herself to stand tall, glaring at the sky.

Morgan's Falchion flared brighter, pushing back against the malice cloaking the world.

And S'yne?

She let out a soft sigh and wiped her lips. "...I will forgive you this once, Mister Naofumi. Please warn me next time." Her ears flushed red as she said, "That was not unpleasant. But a lady needs to prepare her heart..."

"Sorry. Also, he's charging up again."

S'yne nodded. "I am aware. In that case..." She flicked her wrist, causing her small sewing kit to turn into a giant spool. "...Shall we collect more material, Mister Naofumi?"

Lightning crashed down from above, the Fell Dragon clearly trying his best to get rid of us.

But S'yne just smiled and casually spooled the lightning into an ominous violet thread that looked covered in oily black mist.

Lucina watched it all with disbelief. "...It is that simple?"

S'yne shrugged. "Mister Naofumi is currently giving me all of his essence-"

I coughed. "Phrasing."

S'yne gave me a side eye. But then she sighed and said, "Soul power, I guess. As for how much that has strengthened me..." She looked up at Grima and smiled. "...I have always wanted to work with true dragon leather. Shall we see if we can harvest some?"

*YOU DARE?!*

S'yne giggled.

And then there was a white blur and she vanished.

A second later, a white streak started carving across Grima's scales, followed by a furious roar.

And watching it all...

"Huh. I guess her power basically is Minecraft. Isn't she just flying with an Elytra and trying to kill an Ender Dragon?"

...I realized once again how convenient it was to mix game mechanics with reality.