Mahiru looked at Adrien for a moment. "You said other races would try to recruit me, but that's exactly what you're doing too."
"Yes", Adrien answered frankly, he didn't have a reason to lie here, "your sacred gear is probably strong so you have a lot of potential, if you join me it will make me and my peerage stronger."
Mahiru went quiet. What Adrien said hurt her a little. For a moment, a bad thought crossed her mind. Had he been kind to her this whole time just so he could use her?
But she quickly pushed that thought away. Adrien had said he only sensed her Sacred Gear a few days ago. That meant all the times he took care of her and stayed by her side were genuine. Adrien really was a kind person.
The night he let her sleep in his bedroom while he slept on the living room sofa. The times he helped her in the kitchen and took her out to eat. All of that showed who Adrien truly was.
So if there was anyone she wanted to trust and ask for help, it was the devil standing in front of her. Her first true friend.
She smiled, "Can you explain more about the peerage thing".
Adrien noticed her expression and smiled back, he understood that she trusted him.
"There is a system called Evil Pieces, created by Ajuka Beelzebub, one of the Four Great Satans, after the Great War to restore the Devils' numbers. These pieces are used to reincarnate people as Devils, whether someone who died recently or someone still alive who willingly accepts it. The system is based on chess, and a full set has 15 pieces: 1 queen worth 9 points, 2 rooks worth 5 points each, 2 bishops and 2 knights worth 3 points each, and 8 pawns worth 1 point each. Together, these pieces form the peerage of a high-class Devil, meaning the group of servants and allies under that Devil."
Mahiru listened intently to Adrien's explanation, she understood the basic premise of it, but something bugged her, he called reincarnated pieces, 'servants'.
"What did you mean by servants?"
"Yes, you would become my servant. But I would not force you to do things against your will, so it is mostly just a formality. Still, if it is about the supernatural world, you would need to listen to me and do what I tell you to do."
Mahiru nodded, "Eum sorry to ask so many questions, but is there any side effects to it?".
"You'll feel a little weak and tired during the day because of sunlight, but you'll get used to it over time. You'll also gain a pair of wings, though you can hide them tuck them in you." Adrien thought for a moment, then added, "you'll live for like ten thousand years, gain demonic powers, and become much stronger. I'll even give you land in the Underworld."
Mahiru's eyes widened slightly. Live for ten thousand years? Become a landowner? Then she looked at the man in front of her. Did that mean she would stay by his side for that long too? Her ears turned red as she started daydreaming.
Adrien tilted his head slightly, "what are you thinking about?"
"N-nothing!", she shouted.
Mahiru thought for a bit more. The advantages outweighed the disadvantages. Anyone might think she was crazy for thinking like that, she was basically selling her soul to the devil. But she liked and trusted that devil, so she did not care. She had known him for only two weeks but she wanted to stay by his side. She wanted him to help her, teach her, and protect her. She liked Adrien. No, she loved him.
Mahiru looked at Adrien's pale green eyes, she felt warmth when she looked at them, it gave her the feeling that everything was going to be alright. She suddenly nodded her head, "Adrien, I want to be with you."
Adrien smiled, he lifted his arm and patted her head.
"Then we'll start the reincarnation ritual right away, so you'll have time to get used to your new powers before you go to school tomorrow".
Adrien motioned for Mahiru to follow him. They stepped into the living room, and with a flick of his fingers, he cleared some space in the middle of the room. Mahiru stood in the open area, and a dark blue magic circle formed beneath her feet, its shade slightly darker than his sister's.
A chess piece formed in Adrien's palm. It was a bishop piece, worth three points. "The energy that leaked from your Sacred Gear didn't really feel like it was connected to swords, so I think the bishop piece would suit you best."
Adrien smiled, "Ready?"
Mahiru nodded. The magic circle flashed and the ritual began.
"Mahiru Shiina, I call your name and offer you rebirth. By the power of my peerage and the will I place into this piece, cast aside your former self and awaken anew as a Devil. From this day on, you shall stand under my protection and by my side. Rise, my Bishop."
The bishop piece floated toward her and entered Mahiru's chest. Right away, she felt a strong pressure spread through her body. It was not painful, but it was very uncomfortable. After a few seconds, the magic circle started to fade, and the pressure slowly weakened until it was completely gone. Mahiru's legs lost their strength, and she fell forward, but Adrien caught her. She looked at him with a soft smile, then fell asleep in his arms.
Adrien felt a small amount of power enter his body and merge with his demonic energy reserve. It was less than one percent of his total power. He was an ultimate-class devil after all, so the power gained from reincarnations did not affect him as much as it would affect a high-class devil.
Adrien was born a High-Class Devil. He did not have as much demonic power as Sirzechs Lucifer, but his unique constitution made him the greatest talent the Underworld had ever seen. By the age of eight, he had already reached the Ultimate-Class rank. However, that fact was never made public. The only ones who knew were his family and the Four Great Satans. To the rest of the Underworld, he was simply seen as an exceptional genius for being born that powerful, but no one truly knew how far his talent went. His fight against Riser was the first time he had ever fought in public.
So why did Adrien not already have a complete peerage, if he had basically been eligible to form one since birth? The answer was simple: he did not want one. He refused to accept the Evil Pieces, saying they did not interest him. Back then, he spent all his time trying to escape Agares Island to explore the world and cause all sorts of trouble for his family. Then, at sixteen, about a year ago, he finally applied for his Evil Pieces and was accepted without even needing to take a test.
That meant it had only been one year since he started searching for servants who matched his standards. He had used one Pawn on Lynn, and now Mahiru had become his second servant, his Bishop.
Adrien laid Mahiru on his bed to let her rest, he covered her with a blanket and left the room. Suddenly he felt an eary feeling from the city, but it dissipated as soon as it had appeared.
"Must've been the wind", he shrugged. He sat on the sofa and turned on the TV. Jujutsu Kaisen had dropped the final episode of the season, and he was gassed to watch Yuta destroy everyone in the Sendai colony and prove his fraud allegations wrong. And what an episode it was!
--<>--<>--<>--<>--<>--<>--<>--<>--<>
Mahiru slept through the entire day and only woke up in the evening. Once her mind fully cleared, she immediately felt a new power flowing through her. It was overwhelming, far greater than anything she had ever felt before.
She clenched her right hand into a fist and felt a surge of strength. Then she got up and walked into the living room, where Adrien was studying something at the table.
"Oh, you woke up. How do you feel?" He asked.
"Very strong", Mahiru smiled.
"Yeah let's see your enthusiasm tomorrow morning," Adrien snickered.
"What are you doing?", Mahiru asked as she peeked at the notes in front of Adrien.
"I'm working on a sort of magic circle", he answered.
"Oh! like the one your sister used?".
"Nah, that one is just a basic teleportation circle that anyone can use. The one I'm working on doesn't need to be cast and doesn't require any demonic power."
Mahiru had only been reincarnated that day, so she had no idea what he was talking about. Noticing her confused expression, Adrien smiled slightly. "Have you ever watched Naruto?"
"Eumm... no."
"You should, it's PEAK. Since you haven't watched it, I can't really explain what I'm basing it on, but once it's done, you'll understand." Adrien said.
Adrien closed his book note and looked at Mahiru, "Ready to awaken your Sacred Gear?"
"Wait right now?"
"Yeah, the sooner the better. Now that you have demonic power it will be easier to awaken it too. Just close your eyes and visualize the strongest thing that comes to your mind."
Mahiru was taken aback by how fast everything was going, but she still did as he said. She had to think of the strongest thing she knew, and her mind immediately went to someone she had always admired while growing up: her helper, Koyuki-san. No matter what was happening around her, Koyuki-san was always there, helping her, taking care of the house, and managing the other helpers. Because of that, Mahiru truly looked up to her.
"Whatever you thought about, try to manifest it in front of you".
"Manifest it?" Mahiru had no idea how she was supposed to do that, so she went with the simplest approach and just imagined Koyuki-san appearing in front of her.
A sudden flash of light appeared around her wrist, and a bracelet took shape there. It was silver, decorated with pink jewels. Adrien took Mahiru's hand and examined the bracelet from every angle, then a smile slowly spread across his face.
"Not bad, that's a strong Scared Gear, just as i expected." He was fairly content.
"Do you know what it is?", Mahiru asked.
"It's called Sanctum Veil. It's a barrier-type Sacred Gear that lets its user create a protected zone around themselves. Rather than acting like a simple shield, it forms a defensive territory, almost like a moving sanctuary. Tomorrow after classes we'll go somewhere for you to train using it".
"Can't we go now? I don't feel like sleeping, I just woke up".
"Hmm... Nah, tomorrow would be better, I wanna continue working on my project. In the mean time, try to gather your demonic power there". Adrien said as he pressed his finger against the hollow of her throat.
"Why?"
"Just do it, I'll explain it later."
Mahiru pouted and muttered, "you always say that".
They spent the night training separately. Mahiru sat cross-legged on the sofa, meditating and trying to gather her demonic power in the hollow of her throat, while Adrien drew magic circles in his notebook.
After a few hours, Mahiru fell asleep on the sofa. She had exhausted herself by trying to control her demonic power for the first time. Adrien sighed, "This shit is becoming a habit at this point".
He took her to his bed, he would normally leave her alone in his bed, but he became her master and she was his servant now, so he had no reason to sleep on the couch anymore. The bed was large enough for two people to sleep very comfortably in anyway.
Just as he was about to lie on his bed he felt demonic power surge for half a second from the west, then it completely disappeared, leaving no trace behind. Adrien spread his senses across all of Tokyo, but found nothing.
He narrowed his eyes, even if he went now, the mysterious person would have disappeared.
He sighed, 'What a drag, I'll deal with it tomorrow'.
----------------------------------------------------------
Mahiru's sacred gear was an original one, I didn't use one from the original story.
I also changed the fact that Adrien met Lynn when he was 14 not 9, to match the time he got his Evil Pieces.
Comment here if yall want R18 stuff, though I won't go into full smut and detailed sex, just so you know.