It Started With Devils & Artefacts

The group of girls truly wanted to stay and watch how Marcus worked. But… They have school! And since Serafall is here and they didn't want to look like they are incompetent and can't do their duties properly.

Especially since they were the ones who asked to come to the human world in the first place! They needed to attend their classes. Thus leaving the Genius inventor alone with the Satan.

It was the first day of human school for Rias and Sona, but their minds were not on the classes.

All they could think about was the guy downstairs setting up a surveillance system for their town. Especially since Serafall has hyped him up so much, they needed to see him work!

And so the moment the last bell rang, they rushed downstairs to see what was going on.

…

…

…

"What is that!?" Rias asked with wide eyes.

"It looks like a diamond…" Sona said while adjusting her glasses.

"I know it looks like a diamond, but diamonds don't glow or emit white glowing particles…" The redhead said with an eye roll. 

"True. And I am just telling you what I see." Sona snark back as she shrugged.

After their small shock, they walked into the room. Looking around, they could see that it was now some sort of a ritual room combined with a sort of Sci-fi reactor type room.

Some types of Glass panels were spinning around the diamond. The two devils assumed that they were absorbing the magic energies which were being emitted by the diamond-shaped thing…

There were also runic carvings spread throughout the whole room. Walls, ceiling, ground. Nothing was spared, and by this point; the pair were wondering just how quickly this man worked. Even a devil takes his time when doing rituals like these…

Yet, he did all of this during the time they were attending classes.

"Ummm… I thought Barrier things like that are magical… Why is there a computer terminal of  sorts there." Rias asked Sona with a confused look. 

"Why are you asking me? You think I have a clue of what's going on here?" The younger Sitri almost hissed at Rias from annoyance. And frankly, she is feeling quite inadequate. She saw runes from at least 3 different cultures, and she can bet that there were others that are from different supernatural cultures as well.

Meaning that Marcus knew more than her! And she spent most of her life in a library! Her brain was trying to come up with some sort of explanation on how this is physically possible…

"I thought you knew more than I did…" Rias said with a casual shrug.

All she got back from her friend was a hiss. The younger Sitri just hissed like a cat at Rias, who found it incredibly amusing.

"No I don't… this is beyond me," Sona said to her redhead friend before looking around for the teen inventor. Moments later she finally found Marcus.

The genius inventor was sitting in front of a table with a futuristic laptop on top of it. There were several cables connected to it, these cables were also connected to the Diamond-shaped barrier reactor.

Sona then saw her older sister sitting on the table with a book in hand. Meaning that her older sibling was here the whole time.

All the younger Sitri could think of this situation was that, yes… The Satan Leviathan is pretty much infatuated with a human inventor to the point that she spends the whole time with him regardless of anything…even work...

She wonders what would happen if the people of the Underworld learned of this? 

A shiver went down. Just imagining the chaos. One of the most powerful devil females infatuated with a human.

"You two are here. Nice. Come over. Let me explain some things." 

Hearing his voice both of them were stiff for a bit. Nonetheless, they quickly went over.

Serafall lifted her head from her book and looked at the pair. She smiled before going back to her book.

Sona didn't know if it was a good type of smile or a bad type of smile… Well, time will tell.

"First the barrier core." Marcus pointed at the diamond-shaped core casually from his chair. And yes, it was a comfortable PC chair that he got from somewhere.

"The official name is the Diamond Core Heart. It's something I have designed and created myself. The core reactor was carved with magical intent to give it more sturdiness. It has three protection layers. Since this one has a slightly different purpose from mine, the first two layers are spread throughout the whole city.

The first layer is surveillance, the magic  that spreads throughout the city observing its population. Once a certain threshold of magic is reached, the magic will react to it and let you know. This is where the second layer comes in place. Observation. Once that threshold is reached, the magic will show you who it is and where it is. And lastly the third layer. The third layer is protection. It can only be activated manually from this area. It turns school into a fortress that even Ultimate Class Devils will have an issue with breaking through." Marcus gave a long yet brief explanation without even breaking his facial expression.

Both listened with abrupt attention. The pair were quite fascinated and awed by what they heard. This thing protects against ultimate class devils attacks?

"Where does it get its power? I do believe the Shinto Pantheon will be...dissatisfied if they learn that we drained Japan of magic to kick start this…" Sona said with some concern.

"It's based on Marcus M.T.M technique," Serafall said from the side as she was playing with her.

"What do those letters stand for?" The younger Sitri was very curious about this... technique.

"Motion to Magic. The core was kick-started by a motion that created magic. Once that is done that magic enters what is called a loop of magic creation. A loop-based reactor. In other words, it creates magic from nothing… and it will last forever." The older sister of Sona explained with a casual shrug.

"So you did listen to my explanation," Marcus said with faked awe.

"Of course I did!" She exclaimed, almost angrily.

"Well, it was hard to tell, especially since you were spacing out." The genius inventor shrugged at her.

"Of course I was spacing out! You just told me that the reactor will last as long as the planet! I was shocked and awed and all the other stuff when one is gobsmacked…" The Leviathan said that in a single breath.

"Hmm… right, well I went through that days ago when I finished the maths behind it. I guess you need real proof." He said with a shrug.

"Hmm? Are you still awed by your stuff?" She asked curiously, forgetting about previous comments for a moment.

"On a theoretical level. When I realise that I got it down and the item's possibilities." He explained to her as his gaze returned to the pair who were listening attentively to what they were saying.

"Now for the part in which I need you two," Marcus said as he got up from the chair and started walking towards the computer terminal.

"I will add you two into the system. At this moment the Core is only working in this room. To make it citywide you will need to send your peerage members to mark the boundaries of the barrier."

"I understand/I will do it." Both nodded and answered at the same time. Marcus prefers them this way, after all, he watched the anime and knows how these two can be and how much trouble they can end up in.

Now, it will be even better. They are going to get monitored by him 24/7… meaning that, the moment they are slacking in their jobs he can instantly report to either Venelana or Serafall. He might not be their father but they are part of his tests… and he has fired people for less in his previous life.

"Good to hear." He nodded at their response before walking over to the computer terminal and starting to press buttons on the screen.

"It's a touch screen!" The redhead whispered at Sona. Who nodded, looking very curious. All she could see were letters and numbers on the screen. She has no idea what is going on.

That was until the screen went dark and then restarted itself.

This time the screen showed 'Aurora Borealis', before the lights formed into letters showing 'Aurora Terminal v1.0'.

Seconds later the letters faded out and showed a very futuristic terminal. To Rias, It looked like something ripped right out of an anime or a video game.

She could see the terminal taking readings from the diamond core. Showing them in numerical values and lots of spinning icons… the redhead felt that it was… way over her head.

After pressing on the terminal Marcus looked back at the pair.

"Put your hand on the screen. It will register and link you to the barrier." After saying that he took a step back and made some space for the pair.

Both of them nodded seriously. It looked like they were about to do something intensively big… the genius inventor internally rolled his eyes.

The first one to step up was Sona, she looked at the screen and saw a window that said [Register New User] and below it was a simple image of a palm.

She figured that she had to put her hand on that specific area.

Without wasting any time she put her hand on the image. Instantly, she felt some drain on her magic.

Her eyes widened. That moment she knew that it was a seamless magical machine!

She could not even see the difference between magic and technology by this point! It was just that good!

Soon enough she saw her image. And a full 3d profile has been constructed on her! even her occupation has been filled up! This was the most powerful registering tool she has ever seen.

[User Number: 01]

[User Name: Sona Sitri]

[User Species: Pureblood Devil From 72 Pillars]

[User Occupation: City Overseer]

[User Clearance: Barrier User]

"It did all that from just taking a bit of my magic?" Sona asked with sweat rolling down her forehead. This stuff is incredible!

"Indeed. It was reading your magic. Now Gremory you're up next." 

Hearing that. The younger Sitri walked away and gave some space for Rias. Marcus quickly set it up to register for a new user once more.

The redhead quickly did the same as her best friend. Only that, she didn't mingle much in front of the terminal. She was very satisfied seeing how perfect the 3D copy of her was.

[User Number: 02]

[User Name: Rias Gremory]

[User Species: Pureblood Devil From 72 Pillars]

[User Occupation: City Overseer]

[User Clearance: Barrier User]

"Now that you two are connected. Let's test it out." He said that before looking at Serafall.

"Sera, make your presence known."

Hearing his command the Leviathan called forth her magic.

At that moment both Sona Sitri and Rias Gremory experienced something akin to a vision.

They saw Serafall channelling her magic in the basement next to the Diamond Core Heart.

"This is incredible… Will we be able to sense anyone in the town?" Sona asked while making sure her glasses didn't fall off. Now she understood the full scale of this barrier system.

It's simply priceless! 

Serafall smiled seeing how her little sister finally understood what this meant.

"Indeed. The moment someone raises their power beyond a certain level, it will react. I made it especially potent against non-devil magic users. Meaning that you will be notified the moment someone like an angel or a fallen angel appears in the city." Marcus explained to them.

"This is incredible… it's like a system of some sort of barriers!" Sona said after realising what this means.

Serafall smiled for a bit. If only her baby sister knew that this was based on the Heaven system! She would probably pass out!

"You can see it in more detail if you get closer to the diamond core." He said with a smile. And Sona quickly walked over and got a closer look.

Seconds later the younger Sitri gasped. 

"It's… like a complete ecosystem of some sort!" Seeing how Sona reacted, Rias walked over and checked it herself.

"It's...beautiful…" 

"And complex! Most importantly it's magically based! It's like technology but created through pure magic!" The younger black-haired devil said with the awe of a small child. She then looked at Marcus with stars in her eyes.

"How did you make all those magics from different pantheons work so seamlessly! This is simply incredible!"

"Well they were like a puzzle, the difficult part is figuring out the shape and where you have to place it in a big image." He explained simply.

"But...that should take hundreds of years of studying!"

"Or someone a little bit smarter than normal, finds a pattern and figures it out." He said with a shrug.

"...Yes… 'little bit'…" Sona said, her eyebrows twitching. She had the urge to punch him but she resisted it.

A little bit does not describe what he just did. In layman terms, Marcus basically 'unified' the whole world's magical languages into one universal language and then used it to make the magical equivalent of a computer.

If that's a 'little bit' then she should be considered a vegetable…

And the rest of humanity drooling meatbags…

"Indeed. This is nothing more than a little brother compared to what I have built in my place…"

Sona gulped down hearing that. If this was just a little brother, then how complex and big was the diamond core in his place?

'Wait! Sister said that he has Pantheon worthy protection… Does she mean in the literal sense?' The younger Sitri's eyes widened, and her face pales… 

Now she has started to see truly how much he is worth. No wonder Serafall threatened her multiple times over that meeting.

"...For the next part, I want your peerage members to split up and place these markers just outside the city limit. It will work like boundaries. Once it's done, the Diamond Core Heart surveillance will activate." Marcus pulled out a pair of briefcases from thin air and gave them to the confused pair of girls.

"Inside of these, there are instructions on how to do it. Think of this as the first mission from me as my devil contractors." He said, quite seriously and the pair quickly nodded.

"Leave it to us." Sona professionally said while fixing her glasses, she was going to perfect this no matter what. Same with Rias.

~~~~~~Few Days Later~~~~~~

For the past several days, Marcus has been living in the Sitri Estate in Kuoh.

Even then, Sona had no chance to even have a proper conversation with him!

And it was just infuriating! A man which she sees as the next genius of the millennia is living under the same roof as her and she has no chance to ask… tons of questions!

It was just annoying! Nonetheless, it was partially her fault as well. Because she spent countless hours with the markers and testing this incredible surveillance system! 

Once it was set up she could utilise something akin to the view from the eyes of a bird and check the city from the top. 

It was just that great! Not that her happiness will last for long as she soon realised that Marcus will be leaving. Since officially he was just on a holiday leave. And because Japan doesn't have those two weeks of Christmas Holidays like the European countries do. On paper, he was just on holiday in Japan.

And he will be going back to his country soon. This means she doesn't have much time left! That's why she decided to look for him and… befriend? Maybe get some missions? Learn something from him? This was one of those moments when she didn't quite have the time to even think of a proper plan…

In the end, she arrived at one of the living rooms where she knew he was staying.

She was about to call for him but then she felt her sister's presence! Sona quickly reeled in her magic as much as possible and decided to listen in!

This was the perfect moment to find out how deep of a relationship her older sister has with him!

Slowly she positioned herself so that she could have a look. Leaning close to the wall as much as possible.

Finally, she was able to see him without any obstructions!

And her cheeks instantly exploded with a blush. She saw her sister sitting on his lap in a very intimate position while he was reading something from a device.

"How long do you think it will take for those two to figure out that they can track Sacred Gear holders?" Sona heard Marcus' voice. The younger Sitri assumed that he was asking this to her older sister.

'We can find Sacred Gears with this? Just how good is this Diamond Core Heart?' Sona's heartbeat accelerated just thinking of how quickly she will be able to fill up her peerage if this is true!

"Fufufu… how many secrets did you leave for those two?" 

The younger Sitri blushed more when she heard how seductive her older sister was sounding! 

'Did they already go the whole way!? Damn sister! He is as old as I am! Still though… he is… hot...and...super smart… Well, calling him just smart is an insult… genius maybe? Yes, genius… And his body is…. That confidence…' Sona shook her head. Her mind was going into the gutter! She needs to learn more instead of having these thoughts!

"Quite a bit, they will be able to learn it if they are driven. So, instead of going in circles, give me a non-bias version of what you think." 

The younger Sitri was impressed by how he was holding back against her seductive older sister! She was quite impressed by his resilience.

*Sigh*

"Fine. If you insist. Sona will discover most of the functions first. Since she is more driven than Rias. Who is by all accounts just playing around." The Leviathan explained what she was thinking. Her younger sister was slightly feeling proud of herself that her older sister has such a positive non-biased view of her.

"Gremory is not playing around. She is running away. She believes that all her problems will be solved by themselves. That is what I found out about her. This girl is a classic princess who believes things will fix themselves. Simply put, she is waiting for her hero to pick her up. Once that is done she will start moving." 

Sona paled after hearing that. He already has Rias completely figured out? But, he was not even around her!!!

'What kind of monstrous existence is this guy!?' The younger Sitri felt chills going down her spine!

All she heard was Serafall's laugh.

"That's why I like you so much! You could easily be a Satan!" The older Sister of Sona laughed with an extremely amused tone.

"You must be joking. You want me to govern? I will turn the whole population into test subjects if I become a leader." She heard him say with a dull tone.

Just imagining a whole population turned into test subjects made Sona shiver. This sounds like what a real Diabolic Devil would do!

"Hah! You didn't see Sona or Rias complain! They were excited to test your things!"

That moment the younger Sitri realised that yes… she is already a test subject! And she didn't even realise it!

"Nope. You just want me to become a devil and take Lucifer's position or something…" He said that with a sigh.

Sona could already imagine that. Serafall probably just wants that so that she could flaunt her boyfriend, by that time Husband, to the rest of the devils… more specifically the council…

"Maybe~~~ any girl would want to show off their boyfriend to the rest of the world!" The Leviathan said with a cute voice. By this point, Sona can see that her sister is getting very touchy with the genius inventor.

"And your way is by making me an office worker?" He asked her with a dumbfounded look. He already stopped reading from the device and instead looked at Serafall.

"Who knows~~~ by that point you could revolutionise paperwork. Maybe it would even become an interesting activity…" 

"Hmm, probably, I already have several ideas just by thinking in that direction." 

"See! You can do anything! If you put your mind into it~~~ and you would be the most perfect and most powerful Lucifer if you truly would want it!" 

'Oh by Satans she wants him to reincarnate! Well, that is obvious...but would he?' Sona was shell shocked and at the same time excited and terrified by this idea.

*Snort*

"You need better offers than that. Little Sera…" 

*Slap*

The younger Sitri blushed seeing and hearing that. He just slapped Serafall's ass!

"All I can offer is myself… in any form you want~~~"

'I need to get out of here!' Sona quickly realised what was going to happen next! She quickly dashed off! Her blushing reached a completely different level. Never did she expect Marcus to do things like that to her sister! Who is one of Underworld's strongest and is a leader!

This was beyond anything she could have thought!

~~~~~~Next Morning~~~~~~

The next morning in the living room Sona was having breakfast when her older sister entered the room.

Serafall walked over to her little sister who could not even look at her older sibling without blushing.

The older Sitri leaned forward and started whispering into her ear.

"Marcus gave you a head start yesterday, don't waste it. It's very rare for him to do that. It would seem my countless hours and days of seductions paid off… in some way." 

The Leviathan's words made Sona pale and turn whiter than she ever was.

They knew she was there! They knew the whole time and still acted like she was not there.

"You do realise that you are using his system for tracking, right? The very same one which he designed, created, tailored. We most definitely knew you were there So-tan! That's why, use this moment to gather your peerage." Serafall patted her little sister's head before going to get some coffee…

"Sister… isn't he the same age as me? And you…"

The black-haired Satan started laughing after hearing that.

"If you use age like that So-tan, then you very much have wasted your life... and me? I should kill myself for wasting centuries…

Just don't… don't... use age to measure him… otherwise, you will lose any drive you have for anything… because you will feel inadequate." The older sister said to her younger sibling very seriously. 

"...Yes… I suppose you are right… it's just so difficult… while we were spending- wasting time in classes he put that core in the Academy basement… I felt like I wasted my day!" Sona said angrily, forgetting what she saw yesterday.

"You felt that just by being next to him in a day. I have spent the past three years with him, Sona. I saw him make everything and I know how you feel, even more than you can imagine. By this point, I realise that you have to focus on what you are good at. I know I am good at reading people as I am the one who is responsible for the diplomacy of my race.

If his achievements make you feel like that, then use that to make yourself better." Serafall said from personal experience. She felt very much completely weak and even pathetic in front of a teenage human… it was an experience she doesn't want anyone else to feel. 

"... I see… thank you for giving me advice sister… it's nice to have you around like that…" Sona said with a small embarrassed smile.

"Oh...So-tan is so cute~~~" Serafall hugged her baby sister…

"Gah!!! Release me! Y-You smell like man's perfume!!!" Sona said with a bright red face after getting out of her hold.

"Hehehe~~~ embarrassed?" The Leviathan said with an amused laugh.

"Y-You should get a shower, you will be going to the office today right?" The younger Sitri said with a flushed expression.

"Don't worry~~~" The older sibling said in a sing-song voice, she started walking towards the kitchen ignoring the previous comment.

~~~~~~Marcus~~~~~~

[Target Located]

[Unique Magical Signature detected]

[Scanning…]

…

…

...

[78% Visual fit according to the previous description of the target.]

[Possible 'Longinus' Boosted Gear host found!]

I lifted my Aurora glasses after reading the latest notification.

Finally, I have found the target. Finding him like this was annoying … for the simple reason that his magical signature was that weak. It's even below regular humans…

So he was like… swimming below anyone's radar…

But, there is an easy way to find him. Just apply a specific filter and he will stand out like a sore thumb. There is only one guy in the whole of Kuoh who has that below-average amount of magic.

After finding him I did some tracking and Aurora did some routine observation. Building up his daily schedule, after that was done I went to the location of which, he would most likely pass and simply waited for him.

Putting on my glasses I tracked him through Diamond Core surveillance.

Seeing that he was quite close I pressed a button on Castor's handle and a thin card-like object came out. That was the cartridge. Storing it into my cartridge deck, I pulled out another and inserted it into the gun.

[Castor loaded with Stun cartridge]

Reading the notification and dismissing it mentally, I simply waited while leaning against a wall.

A few minutes later I saw a brown haired teen with a silly grin on his face walking towards the road of which I was waiting for him.

He was going home after watching hentai with his two idiot friends. Going home quite late… alone… the best time to mug someone… but, this is Japan. The crime rates are extremely low. So, the perv is not even afraid of going home late…

Nonetheless, this time it's going to be different…

Lifting Castor, I pointed at him and pressed the trigger.

"Hmm?"

The brown-haired teen turned around and saw a bolt of electricity slam into him.

His whole body twitched as quite a bit of electricity smashed into him.

Before collapsing on the ground.

I holstered the gun and walked over. Aurora did a scan on him through magic, the guy was perfectly fine, his body just went into an unconscious state.

I got on one of my knees and put my right hand on him. Several white magic circles appeared around him. I quickly did a quick scan, checking if he truly held the Boosted Gear.

"So, it is. Good. This means that I didn't waste 30 minutes of my life waiting for this waste of oxygen." I stopped with the scan. While mentally connecting to Ars Goetia.

"Sera, come to me," I said while getting back on my feet.

Moments later a Leviathan circle appeared next to me and Serafall was now standing next to me.

"Master? Where… who is he?" She looked around before spotting the downed pervert.

"Meet the Red Dragon Emperor," I said plainly.

"W-What? He is this generation's Red Dragon Emperor!? But, I can't sense anything from him!" She exclaimed for a moment while focusing on the downed form. Her senses were digging into him.

"Put your hand on him, send some magic to check," I said with an eye roll.

Sera did just that as she scanned him properly.

"Yes… I can sense faint dragon energy… how did you even find him!?" She stopped with her scan and turned around to look at me.

"I found him when I did a scan of the city's population. He has a remarkably low...extremely low amount of magic. But for some reason it emits dragon energy. So a check later and I found out that he is this generation's Red Dragon Emperor." I said with a shrug.

Before getting serious.

"Take him to Sitri Estate. I will do a proper scan on Boosted Gear over there. He will make a perfect subject for those two girls. I want to see which one of them will find him first and recruit him as their Peerage member."

She stumbled for a bit after hearing that. Nonetheless, she cast an extra sleeping spell on him before sending him away in another magic circle.

"That's quite devil-like of you. Treating a poor little human-like some test subject. You truly would make a good Satan~~~. Still though… how do you know he will accept being in a peerage after unlocking his Boosted Gear?" Serafall asked me as she leaned forward to cuddle with me.

"Because his dream is to be the Harem King. And he has said that at least 6 times in the past 3 days and mentioned Oppai at least 47 times in a single day... today… he is the perfect individual to be exploited by a devil. Promise some 'Oppai' and a Harem and he will be willing to sell his soul." I said that with a dull voice.

Nonetheless, I gave the glasses to Serafall to read over the file on this guy…

"This... Issei Hyoudou… what a… weird human he is… my money is that he will be Rias peerage member… my So-tan would probably kill him or trade him the moment she can." The Leviathan said with an amused look.

"True. Still, I want to see who will discover him first." I said that while wrapping my hand around her waist.

"Yes. This will be a good test for them, with the prize being a Longinus user in the peerage. It would seem your visit here isn't as dry as you thought!" The black-haired devil lady said with a happy tone. She took off the glasses and looked very happy with this development.

"Yes. It's quite fascinating how many Sacred Gear users are in this town." I mentioned the weirdness of this place, before focusing on the matter at hand.

"Why don't you take me back? I still need to scan that pervert and drop him back in his house."

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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