The Substitution of the Shield Hero

Nightfall in the other world.

Lia idly tapped False Mercy against Kazuki's face and said, "Did you break already? Come on, let's have some more fun. I'll even let you attack first!"

Kazuki looked up with blank eyes. His ponytail, which had been neatly tied up at the start, had unraveled, making his hair disheveled. "Please, Miss... Let me go..."

His armor was completely in tact. His sword was in pristine condition. But it was clear that his spirit had completely broken.

Bahamut walked over and raised an eyebrow when he saw the condition that Kazuki was in. "...Big Sis. Did you really have to do that much?"

Lia puffed her cheeks and said, "He was pretty good! I wanted to see if he would train properly with me! False Mercy is a really useful training weapon, you know? Since it won't let you die, you get to experience death and learn to dodge it!"

At that time, Sylvia walked over, followed by a tired Tsugumi, Kazuki's companion.

Sylvia took one look at Kazuki before sighing and saying, "Lia. You know that normal people aren't used to our way of training."

Lia crossed her arms and said, "I don't get it though! Naofumi-dono said you get better when you face death and win, right? So then if you get the chance to fight against someone whose blade won't kill you, isn't it a great training opportunity?"

Kazuki let out a bitter laugh as he stumbled over to hug Tsugumi. "...Monsters. All of them, Tsugumi. Monsters."

Tsugumi hugged her longtime friend and master before saying, "I know, Kazuki-sama. I know."

Daji watched the dramatic reunion as well as Lia's complaints from the side. Then she chuckled and said, "Well. Regardless of the results..." She looked at the ruined capital of Raybul, which was dotted with temporary campfires. "It seems we certainly made our first mark in this world. I take it they surrendered?"

Sylvia nodded. "Yes, Mother. I... politely explained the situation to them as well as described Libertas. While there was resistance at first, when the inhabitants realized that those who genuinely decided to become a citizen of Libertas and who designated their territory as belonging to Libertas was healed and also protected by Master's abilities, it quickly spread."

Bahamut looked surprised and said, "That still works in this world?"

Sylvia looked amused and said, "Did you really think that Master's influence would be restricted to a single world?"

"...True." Bahamut laughed. "Dad is a bit ridiculous like that." He looked up at the moon and said, "If he was here, he would probably go terraform that too."

Kazuki flinched, his eyes snapping wide open as he looked at the full moon before looking back down at Bahamut. "...Your father has the ability to terraform the moon?"

Bahamut let out a fanged grin. "Not just 'ability.' He has done it once already."

Lia nodded. "Mmhm! Naofumi-dono painted the moon with his colors and even planted his seed there!"

Sylvia facepalmed. "Lia... we need to work on your phrasing."

"But it's true!" Lia puffed her cheeks. "He made Iggy on the moon, didn't he? And the moon incubated her seed until she was born!"

"...Are you doing this on purpose?" Sylvia murmured. "You must be. You cannot seriously be saying this without knowing what it means."

Kazuki slowly blinked. He processed what Lia said. And then his eyes rolled up in his head and he fainted.

"K-Kazuki-sama!" Tsugumi knelt down to embrace him. "W-Wake up! You cannot faint here!"

Bahamut stuck his hands in his pockets and said, "Well... I think this place is settled, right?" He looked at Sylvia and said, "Big Sis Sylvia. Do you know where we are in this world? And where Mein is?"

Sylvia nodded, idly resting her hand on her rapier's hilt, sheathed at her right side. "I do. It seems that we landed in the no man's land just north of a country named Raybul." She nodded to Kazuki and said, "This is the homeland of this summoned hero... though he has yet to obtain a weapon of any kind. It is also home to the Vassal Katana, which..." She shifted her tunic to reveal a katana resting on her left side. "...Immediately pledged allegiance as well as gave all sorts of amenities after I politely introduced myself. And the fact that Master would be very interested in seeing what it was made of if it did not behave."

Daji walked over and rubbed her chin, intrigued by the Vassal Katana. "Fascinating. A spirit sword? Or perhaps something similar, but carrying a fragment of the world's will..." She idly flicked the Vassal Katana's hilt, making it shudder with what sounded like audible fear from how much it shook.

Sylvia rested her left hand on the Vassal Katana's hilt and said, "Be still."

The Vassal Katana froze, clearly terrified to find out what would happen if it didn't obey.

Bahamut chuckled and said, "Well. I suppose it's smarter than most weapons. The Vassal Book didn't show that it was useful, so Dad scrapped it."

The Vassal Katana didn't move. But even so, it radiated an aura of absolute despair. Somehow.

Lia giggled and walked over to poke the katana's hilt. "It's okay! Naofumi-dono won't take you if you're Sylvia's!"

The Vassal Katana seemed to relax. The glittering crimson jewel on it softened to a dim glow.

Sylvia hummed and said, "It is a good side arm, at least. Half-decent at stabs and good at slashing." She tapped her rapier and said, "I've been getting by with this since it's quite sturdy. But slashing has always been a weakness of mine without using magic."

Lia nodded. "Mmhm! We'll just have to get you practice then. Right, Katana-san?"

The Vassal Katana's jewel glimmered, as if excited.

Bahamut watched it and smiled. "That's interesting... If the Vassal Weapons are sentient, and the Legendary Weapons are also sentient... I wonder if Dad's Legendary System is sentient."

Silence.

Lia's eyes widened in understanding. "OH MY GOSH!"

Sylvia looked genuinely concerned. "...If it is, then it has been learning everything from Master."

Daji chuckled. "Oh my... A Legendary weapon capable of extreme versatility and influence learning from a man such as Naofumi who cares about human liberty and volition as an absolute right, but also who gives little regard to those who cross him..."

Bahamut nodded. "I can't wait until Dad realizes it. Especially if it starts talking back to him."

Sylvia sighed. "Well. Whatever the case may be..." She focused and said, "Continuing on with the previous conversation about this world's status... it is in quite dire straits. Unlike in our world, where the four kingdoms were at least prioritizing defense of the world against the waves, this world's kingdoms for the most part have devolved into self-interest, treating the waves as a means to strengthen their forces instead of a serious treat."

Daji's eyes narrowed. "...Fools."

Sylvia nodded. "Mmhm. A few of the Legendary Heroes have been killed already, and the last one was apparently lost in an 'Infinite Labyrinth'... Although that would be Miss Kizuna that they're speaking of."

Bahamut rubbed his chin. "In that case, they don't see the waves as a problem, but as a portal. If I'm right, they probably want to gather their forces and invade our world, right?"

Lia let out a cold laugh. "Dummies. They can't win."

Daji laughed too, fanning her face with a white fan. "My, my. Hubris strikes again for men... They will get quite the surprise if they bring their forces across the portal in the next wave."

At that time, Tsugumi, who had been quietly listening while tending to Kazuki, froze and looked up at them. "Y-You speak as if our world's best will falter if they invade your world. How can you be so certain?"

Bahamut shrugged. "I'm fairly certain Dad can send the moon crashing down if he wants. And he's probably gone to another world to defeat a dragon with twisted divinity while using its corpse for crafting materials. Plus he's literally undying. Emphasis on 'undying' over immortal. Even if you kill him somehow, he'd come back."

Silence.

Tsugumi desperately looked at Lia, Sylvia, and Daji in the hopes that Bahamut was exaggerating. And when she saw that they weren't surprised or even slightly in disagreement with what Bahamut said...

Tsugumi fainted as well.

Sylvia sighed. "...I suppose that is the normal response to hearing what Master can do."

Daji chuckled. "It is indeed. And to be frank, I am surprised that Mirellia is so calm with it. She certainly has a heart of steel considering how readily she banters with a man who already uprooted her country once and could casually destroy her entire world if he fancied."

Bahamut smiled and said, "Dad won't do that. He has principles. Those principles being that Grandma and Grandpa would absolutely never let him hear the end of it if he did."

Lia giggled. "That's true!"

Sylvia took a look around and said, "So what do you want to do, Bahamut?" She looked back at him and said, "Master said we are to support you here... I think. At the least, we are here to make sure you do not go *too* overboard. So if you have any plans, at least share them with us?"

Bahamut hummed and took a look around as well. Then he said, "Well." He slowly turned towards a country to the west of Raybul. One that looked almost like a fortress of steel, especially under the moonlight. "That place looks like fun, doesn't it?"

Sylvia slowly blinked. Then she said, "...Please do not tell me you intend to do a night raid on a kingdom that appears to be this world's major military power?"

"I won't tell you, Big Sis Sylvia~" After that, he laughed and took off running.

Lia giggled and ran after him. "Best little brother!"

Sylvia started sprinting too and said, "You absolute menaces! At least wait until morning! It's late! And we haven't even eaten!"

Daji laughed and idly chased them with movement techniques, gliding across the land. "We can eat in the morning, Daughter. And what better way to greet the sunrise than breakfast amidst the ruins of a kingdom that fell to hubris?"

"Not helping, Mother!"