Prologue

It was deep and dark. The man was deep underground, a place devoid of outdoor light. He was swinging a pickaxe there. The man looked shabby, and his appearance suited the dark and narrow underground tunnel he was in. He was quite elderly. There was not a single spot on his face which wasn’t covered in wrinkles, and he had an extremely hunched back. He was wearing a worn-out grey robe covered in the soil and dust from the narrow underground tunnel that made his pitiful state even more seedy. The lantern fastened to his hip was quite old, too, and barely lighting the man’s surroundings.

His entire body was covered in sweat, and his arms didn’t have enough energy even to swing the pickaxe.

He was taking shallow breaths and so exhausted that it wouldn’t even be surprising if he dropped dead at any moment.

Exhausted inside and out, he was all worn out, yet there was a spark in his eyes. He kept swinging the pickaxe as if he were in trance.

Swing, swing, went the pickaxe.

And, at last, there was a loud sound indicating that the pickaxe had hit something hard, and then a part of the earthen wall in front of him fell away. The man opened his eyes wide and looked at what lied beyond.

“Fu…haha, ahahahaha!” the man laughed.

And then he proceeded to swing the pickaxe far more vigorously than ever before. The crack on the wall grew wider, eventually growing wide enough for a person to go through.

The man threw away his pickaxe and leapt into the opening, laughing with his mouth agape. “Hahahaha! I have done it. I have done it at last! The magical energy smells so rich that I can almost taste it! I have finally found it!”

The man fumbled beneath his robe and ripped the necklace he had around his neck off. He looked shabbier than a beggar, and it was the only accessory he had. The necklace had a glass bottle the size of the tip of a lady’s finger attached to it.

He raised the bottle to the center of the hollow, ahead of the underground tunnel. The air surrounding the man started to swirl and slowly began to gather around it. At the same time, an amber-colored liquid started to form within it.

“Highly dense crystalized magical energy that can be seen with the naked eye…! How remarkable! If I have this much, then!”

He placed the bottle on the ground and started incanting in a deep voice. He had been doing that for an hour or so, but his long incantation had picked up momentum as time passed. He’d been murmuring it out weakly at the beginning but was now incanting the spell with vigor.

And then the spell ended seemingly with a scream, the man’s body simultaneously getting engulfed in a bright light.

“The power, is filling me up… So, this is what it feels like to be young!”

Standing there after the light faded away was a virile-looking young man.

There was no trace of the old man with a hunched back and wrinkle-covered face. Standing there was a young man whose back was as straight as a sword. His limbs were filled with energy, and his skin was as smooth as silk. However, there was one thing he had in common with the old man: his fiery eyes.

“Oh, it’s almost full already,” the man said.

The fluid filling up the bottle had already filled 90% of it. The amount had slightly decreased when the man became young, but the speed at which the liquid filled it up was far greater.

The man cast a short spell, piercing the bottle with the amber-colored magical energy that flowed out from his finger.

The bottle grew in size after that, becoming large enough to fit a person.

“This will last for a while,” the man observed. “Now then…”

He cast a spell, this one a bit longer than the previous one, and then swung his arm. A curtain of light touched the walls, looking as if they were being swept over with a broom, and transformed the cave into a dull cellar made of bricks.

He didn’t stop there, either. He bit the tip of his finger and started drawing a magic circle on the ground with his blood. He then gently ran his hand over it to check if it was drawn well before beginning his incantation.

The spell was longer and far more complex than the one he had cast earlier to de-age himself. Beads of sweat started forming on his forehead, and his face twisted in agony.

The air vibrated, putting the flames of the lantern still attached to his hip out. The room, which had previously been filled with silence, was now filled with a sound like the pulling of a bow.

The darkness, the most dominant force in the room devoid of light, started moving as if it had a will of its own, and slowly began to materialize.

That shadow was darker than the darkness itself, and it bore a clear shape…

It then spoke in a bell-like voice. “Are you the one…who has summoned me?”

What had appeared in front of the man was a captivatingly beautiful woman dressed in rather revealing clothing. Her elegant dark hair grew long, flowing over her white skin. Her slim limbs, too, grew long. She was slender, yet her bust and hips had volume, greatly emphasizing themselves.

“Indeed.” The man nodded at her query.

“I see,” she replied. “In that case, I shall show you a most wonderful dream as thanks for summoning me. Would you be so kind as to erase this magic circle? I won’t be able to kiss those wonderful lips like this,” she whispered seductively, seemingly begging for it.

The man sneered at her. “I cannot do so. If I erase that magic circle, you’ll be set free, immediately bereave me of my soul, and return to the demon realm. I shall erase the magic circle upon the completion of our contract.”

The woman’s expression changed after he said that. It changed from the face of a weak, pitiful girl to the shameless face of an experienced prostitute.

“You are no fun,” she fumed. “It was just a little joke. There’s no way a sorcerer who could gather this much magical energy would fall for such a simple trick, anyway.”

The demoness, sitting in the air as if she were sitting in a chair, crossed her legs. Whether she did it on purpose or not, her movements were both captivating and lewd at the same time.

“So? What should I do?” she asked. “Do I need to suck the life force out of foolish men? Or should I make your enemies have eternal nightmares? I am fine with giving you the night of your life, too.”

“Hm,” the man replied, “I want you to make me a dungeon.”

“Haa!?”

The demoness “fell” from her invisible chair after hearing what the man said.

“Cease that at once,” he commanded. “You are a succubus, so act like one. I can’t help but get turned off even when you spread your legs like that in such sexy attire…”

“That’s not the issue right now!” she exclaimed. “Did you ask me to make a dungeon for you just now?”

“Indeed, that is what I said.” The man nodded. He then spread his arms out and looked around the cellar. “I seek for you to construct for me an expansive, demonic dungeon of massive proportions the likes of which no one has seen before. A colossal dungeon containing innumerable traps, monsters, and treasures waiting within. I want you to construct for me an extraordinary dungeon that will look as if it has dominion over the entire underworld.”

The demoness reflexively massaged her temples. She was a demon and thus did not know of sickness, but this was the first time she’d experienced a headache from something other than being physically hit.

“Let’s assume you had summoned me to protect the dungeon…” she began. “I would have been fine with that since I have been summoned to do that before. But what do you mean by ‘make me a dungeon’!? Leave something like that to a goblin or golem!”

“Of course, I’ll leave digging to monsters like them,” the man replied. “But there are numerous other things besides that that I need assistance with. How should the rooms and passages of the dungeon be arranged? What about monsters and traps? In the case of monsters that are living creatures, they need food to survive. So, who’s going to obtain sustenance for them? When our dungeon grows larger, there will be unpleasant individuals who will come to threaten it. Who is going to deal with them? There are innumerable things to take into consideration and do. That is why I desire your assistance.”

“I understand… But why did you choose me?” the demoness inquired after finally returning to her original position.

The man raised three fingers. “There are three reasons. First of all, I do not trust humans, as they will betray you without fail. Monsters and demi-humans are no different. You demons will try to tempt others if given the opportunity, but you are entirely unable to breech a contract, thus leading me to choose your kind. Secondly, normal demons gain intelligence and strength as they go up in rank; however, they require a vast amount of mana to summon and keep in this world. You succubi are the odd ones out among demons, for you are closely tied with the desires of humans, and your job as a species is to suck the life energy out of them. You aren’t all that strong, but in comparison to the amount of magical power you require, you hold quite a bit of intelligence. You are also well-versed in reading and understanding human emotions. That is why I chose a succubus. And lastly…” The man paused, looked at her, and then grinned. “If I’m going to have someone by my side anyway, then I would prefer for it to be a beautiful young lady, and that is why I chose you.”

The demoness looked at the man with astonishment for a moment and then giggled. “…So that’s it, huh,” she said. “Okay, I’ll assist you with your work.”

“Then agree to this contract with your name,” he told her.

He took a piece of parchment out from his pocket and showed it to her. It all happened in the dark, but it didn’t matter since she was a demon—darkness was a demon’s bosom friend, after all.

“So you’ve already written down the terms of the contract, have you? It seems you are well prepared… And so detailed!? How many clauses does it even have!?”

Fine letters making up the clauses filled the parchment being shown to her from outside the magic circle.

“I’ve already said that you demons will try to tempt others if given the opportunity, so these clauses exist to prevent you from doing so,” the man explained. “There isn’t anything unfair in it that will put you in a losing position, so you need not worry… Although, words alone won’t be enough to win your trust, so go ahead and read it till you are satisfied.”

“There was no need for you to go so far. I would never betray you or anything… Good grief…such fine print.” She muttered some complaints she had, squinted, and looked it over.

“Mm, it looks fine…” she said. “Does this contain words so small they can’t be read with the naked eye? Or has a clause written in special ink that can’t be seen normally? If so, it would invalidate the contract entirely.”

The demoness looked at him with doubtful eyes. The man frowned and seemed offended. “I’ve already told you there isn’t anything in it that disadvantages you. You are quite the skeptical one, huh.”

“You can’t lecture me about that!” she cried. “…Ah well, let’s go forward with the contract.”

“Oh, thou succubus, dost thou agree to give mine thy name, abide by this contract, and be mine strength?”

One’s name held great significance for sorcerers and demons, who were deeply connected to magic. Simply by knowing their name, a being with a certain amount of power could take control of another’s soul.

A contract with a demon made use of that, for it was impossible to be breached by either party upon being sealed.

“I swear upon mine name, Lilushaana, that I will abide by the contract and become thy strength.”

“In that case, I take an oath upon mine name, Ein Sof Aur, that I, too, shall henceforth abide by the contract.”

Responding to their oath, the contract lit up and burst into flames, instantly fizzling out of existence.

The contract had gotten carved into their very souls. Nothing could be added to it or changed now, and thus became set in stone.

“Now then, I’ll be counting on you from now on…” the man said. “You may call me Aur.”

“Alright, alright,” the demoness replied.” I’m fine with being called Lilu… I’m looking forward to working with you, Aur.”

Lilu was about to say I contracted with a total weirdo, but somehow managed to stop herself. They then shook hands after she exited the magic circle.

This was how their dungeon-building days began.

“I’ve been wondering about something for a while,” Lilu commented. She came out of the small magic circle, gave her limbs and wings a good stretch, and then turned around. “What’s this?”

The object in front of her gaze was a huge glass bottle.

It was something Aur had placed there before summoning Lilu.

“That’s… Let’s see,” he said. “I suppose you could call it the dungeon core. It’s going to be the heart of the dungeon we will be building.”

While giving an explanation, Aur cast a quick spell, after which small flames appeared on his palm, then sent the flames to the four corners of the room, illuminating it.

“Do you know what Magical Energy is?” Aur asked.

Lilu answered by puffing up her cheeks. “Do you take me for a fool? I am a demon, you know. Magical Energy is the source of everything related to magic. From sorcery to monsters…and, of course, it is also the source of us demons. It is something that twists, defiles, and changes a bit of this world created by the Creator. That’s what sorcery is, what magical energy is, and what demons are.”

Aur looked satisfied with Lilu’s words as he nodded.

“Then do you know this?” He asked her. “Magical energy is in the soil, in the atmosphere, in water, in living things… Everything that exists has magical energy, but most of it is underground. The magical energy under the ground doesn’t remain stagnant in one place, however. It flows like a path or river, and this path of magical energy is called the Dragon’s Vein.”

“…So, what does that have to do with this?” Lilu asked while touching the bottle here and there. She had a weird expression on her face. It was hard to deduce whether she understood his explanation or not.

“This place is at the center of the Dragon’s Vein,” he informed her, “and this dungeon core can suck up magical energy from it.”

Lilu stared at the amber-colored liquid with widened eyes. The liquid was shining and shaking while being illuminated by the flames.

“Eh,” Lilu began, “is this liquid…magical energy or something by any chance?”

“Yeah.” Aur nodded.

Lilu let out a shriek. “You gotta be kidding me!? For an average sorcerer to concentrate enough magical energy to turn it into a liquid, they’d have to muster up all their strength, and even then, they’d only be able to produce one or two drops! This amount exceeds far beyond the amount of magical energy a human sorcerer can handle… And, how can this be so close to me, yet I can’t smell it? I can even smell minor magic items, so how is it possible for this much to be right next to me without there being an odor?”

“You’re able to smell magical energy, are you? Demons are quite handy indeed… It’s quite simple. This bottle can completely seal magical energy inside it. If there is no magical energy leaking from it, then it won’t produce an odor. You see, keeping this amount of magical energy within my body would quickly render me insane, but it presents no issue if I keep it contained in a bottle and only use it as needed.”

Lilu reflexively looked back-and-forth between the dungeon core and Aur.

“Completely containing magical energy…” said Lilu. “It is an amazing piece of technology. But is something like that truly possible?”

“It is indeed,” Aur replied. “It’s the culmination of my 70 years of research. After all this time, I was finally able to reach this point,” Aur said in a deeply emotional tone.

Lilu was confused as to whether she should be astonished or dumbstruck by it. She eventually picked the latter. “70 years? How old are you really? Ah well, it doesn’t really matter, anyway. I understand the gist of things. If you can keep getting such a limitless, concentrated supply of magical energy like this, then even ruling the world won’t be out of your reach. And that’s why we need to create a dungeon in order to protect this bottle… So, what do we need to do first in this dungeon-building project?”

“Let’s see…” Aur began. “Turn around first and put your hands against the wall there.”

“…? Like this?” Lilu turned around and placed her hands against the wall just as Aur instructed. “Hey, this position is like… Ah!?”

She was about to say something when the sensation of being penetrated made her let out a squeal.

Aur had parted her clothes and pierced her vagina.

“What is it?” he asked. “You aren’t going to say you were a virgin, are you?”

“That’s not it!” Lilu fired back. “Jeez… If you’re going to do it, then at least tell me first.”

Her words were criticizing what he had done, but her voice was already melting like caramel.

“I put it in without doing anything, yet you are quite wet,” Aur commented.

“That’s…um…because…I’m a…succu…bus…ah, that, really hits the spot…ah.”

Lilu was so sopping wet that it was as if she’d been masturbating for hours on end. It wasn’t because…she was feeling good or anything, but rather because she was a succubus. Her body was made for the purpose of having sex anytime, anywhere, and to pleasure any and every man.

“But, it’s unusual…mm…ah, you summoned, me…haa and immediately told, me to build you a dungeon…so I thought, you weren’t interested in things like this…”

“That’s simply a misunderstanding. It’s true that I’m having sex with you now for the sake of building the dungeon, but, aside from that, it isn’t like I’m not interested in having sex. No, in fact I’m quite interested in it. It would be pointless to go through the trouble of constructing a dungeon and obtaining great power and not desire women and great riches, would it not?”

“What’s up with that motive…fufu, ha, a…does it mean…that…mhm…you are making a dungeon because…you want to have sex?”

Lilu giggled while moaning and then turned towards Aur. She opened her legs wide and appeared to be in something of a missionary position. There was nothing supporting her body, yet she was able to do something like that in the air simply because she was a demon.

“But alright…” she said. “If that’s the case, then…nfu… I’ll give you lots of good service.”

Lilu took off her clothes, which were barely covering her up to begin with, and pushed her two ginormous mounds against Aur’s face, simultaneously slipping Aur’s cock deeper into her vagina and squeezing.

“Mm… It’s my first time having sex with a succubus…” Aur admitted. “It’s as amazing as I expected. It feels like…my soul is going to be sucked right out.”

“Nfufu… Thanks,” Lilu replied. “You’re really big, too, and so hard—it’s out of this world…mm, if it weren’t for the contract between us, I’d squeeze all the juices out of you until you had nothing left, but…uuh.” She wriggled her vagina around Aur’s cock and squeezed while moving her hips up and down in midair.

For a succubus, whose livelihood was essentially to wring semen out of men, it would be quite fine to say the organ they could manipulate the most was their vagina. Even Aur, coupled together with his rejuvenated body, was reaching his limit.

“Seems like, it’s a walk in the park for you…” Aur observed.

“That’s because,” Lilu paused, “I am a succubus…ahn… Would you prefer it if, I screamed and cried and acted like I don’t want it?”

For succubi, having sex was equivalent to having a meal. Of course, it was pleasurable for them, too, but it was different from what a human experienced, for they had complete control over their pleasure centers. They didn’t get swept away by feelings of ecstasy and lose their composure, and they didn’t cum unless they desired to.

“I don’t want you to put on such a fake act…” Aur told her. “Ku, I’m going to cum…!”

“Yeah, cum…!” Lilu begged. “Inside, cum inside me…huh!? Eh, wait, this…can’t be! What is this…ah, aaaahaaaaah!!”

Aur released his load into Lilu.

A moment after that Lilu began moaning and her body started shivering. It wasn’t like that fake moan she’d done before. “Wha-What, was that…?”

“They say a demon’s true body resides in the demon realm and thus has no connection to this world,” Aur explained. Still inside her, he started fondling her boobs.

“Eh, ah, wai… What, what is this…” Lilu was bewildered by the sensation she was experiencing for the first time. She tried to escape, but Aur tightly held on to her waist with his arm, refusing to let go.

“They say your consciousness and ego are here in this world,” he continued, “but your body is a mere fabrication of magical energy. Consequently, you won’t feel more pain than is necessary, and even if you were completely destroyed, you’d simply return to the demon realm. It’s truly convenient, but, you see, something made from magical energy can then be meddled with and reconstructed using magical energy as well.”

“Eh, ah, ah, ah, no, stop, mm, ah, ah, aaah…!”

Despite having cummed already, Aur’s cock was still rock hard, and he slowly continued going in and out.

“As such, I’ve reconstructed you in a way that allows you to feel pleasure like any normal human—so you can lose yourself and orgasm. Oh, but I wouldn’t do anything that would harm you, so don’t worry about that. However, I will do things like…” Aur moved his hips and thrust it in deep.

“Aaaaaaah!” Lilu moaned.

“I’ve changed you so we can enjoy this together,” Aur declared.

“Wa-Wait, just a se…wai…nmmuh!” She was short on breath and pleaded for Aur to stop, but he forcefully shut her up with a kiss.

While doing that, he was fondling her breasts with one hand, pulling her closer with his other arm, and topping it all off by giving her vagina a good pounding with his rock-hard rod.

If she were a human woman, she would have felt pain rather than ecstasy due to how intense it was, but Lilu was a succubus—every single movement only led to one thing: intense pleasure that only made her thirst for more.

“It’s definitely better than it was before…” Aur commented. “Aah, it’s great…I’m going to cum…!”

“No, ah, aaah, more, no, ah, ah, aaaaah!” As Lilu felt his cum flowing into her, she bent backwards, shaking uncontrollably.

Aur’s cum was like a strong aphrodisiac for her at this point. If it touched her body, then she’d instantly experience ecstasy, and if it got released inside her, then she’d get hammered with even more pleasure. On top of that, even after cumming so many times, Aur’s cock remained as rigid as ever, and he kept giving her a pounding.

“Wa-Wait, I’ll, go, in…I’ll go, in, san…”

“Go in?” Aur asked. “…Sure, I wouldn’t say no to that. To commemorate the forming of our contract, I’ll make love to you all night.”

“No, ah, mm!” Lilu moaned. “Nooo, uh-aaanh!”

The sexy moans of a beautiful lady reverberated around the underground cellar that still had a long way to go before it could be called an underground dungeon.

…That was how they spent their first night together.