At Y/n's mansion, Y/n was currently napping after a long day of school. But as he slept, he was also training in his mind with Zoa in nature magic.

"Lets rest for now child." Zoa said seeing Y/n was struggling to control the magic. " Thanks to humans polluting the planet, there's a large amount of negative energy in nature. If absorbed too much of, it will drive one into insanity." 

"Then it's best i hold off of learning nature magic for now and focus on on my sacred gears for now."

Y/n began to fade as he woke up, when he did, he noticed Rias sleeping next to him naked, a habit she picked up after he saved he from Riser. After gently getting out of bed without waking her, Y/n flew to the roof to get some fresh air. 

As Y/n relaxed, he noticed something white in the distance. Looking closer, he saw it was a dragon! Not only that, it was flying disoriented.

Spreading his wings, he flew up to catch it. After he lowered it to the roof, he managed to get a better look at it.

"Clear Wing..." He heard Overlord mumble.

"You know this dragon Overlord?"

"Indeed, this is the Clear Wing Synchro Dragon, a heavenly dragon like Odd Eyes and Dark Rebellion. But i never seen her like this before. Overlord said as the dragon changed into her human form. 

She's still disoriented

"I better call Odd eyes and Dark Rebellion."

"That would be the best move."

Y/n let out a slight flare of his powers as a signal, knowing once the two felt it, they'll come his way.

"What can you tell me about her?"

"Of the four of dimension dragons as they like to call themselves, she along with Odd Eyes are the gentler of the four. But she has one hell of a temper if triggered. If she snaps at someone, the language she uses can make a drunk  sailor blush."

"Yikes..."

Soon Odd eyes and Dark Rebellion arrived, Y/n stood back as they helped Clear Wing regain her bearings. 

"Clear Wing, what happened?" Odd eyes asked worried.

"I was flying around in the underworld until i caught a odd scent."Clear Wing explained. "I went to check it out, i found a abandoned and destroyed mansion. When i searched inside, i found a underground lab. And well..." 

She handed them a folder, when Odd eyes and Dark Rebellion looked though it, they began to growl viciously.

"Something the matter?" Y/n carefully asked.

They merely handed him the folder, reading though it, he quickly understood their anger. The owner was mad scientist that crossed the line too many times, having done many experiments on many unwilling innocents. Just reading about it made him sick to the core.

But one experiment caught his eye, a attempt of creating a super devil. The two names caught his attention.

"Kuroka and Shirone... why does the latter sound so... familiar?" Y/n thought to himself.

Before he could think more, he sensed a magic circle appearing behind him. Looking back, he saw Grayfia appearing from it.

"Greetings Y/n, the satan's are requesting you." She said with a slight bow.

"Perfect timing, there's something they need to know about." Y/n told her before turning to the dimension dragons. "Clear wing, you don't mind if i take this folder with me to the satans?"

"Go ahead, they deserve to know." Clear wing nodded.

Soon, Y/n arrived in a meeting room with four people waiting for him. They were the four satan's, Sirzechs Lucifer, the older brother of Rias, Serafall Leviathan, the older sister of Sona, Ajuka Beelzebub and Falbium Asmodeus.

"Y/n, thank you coming ." Sirzechs said. " It concern a Zeroth dragon that's sealed in the underworld."

"I see, i'll get the info about it from Overlord or Zoa, but there's something you need to know." Y/n said before passing him the folder he got from Clear wing.

After reading though it, Sirzechs sighed. "Thank you for bringing this information to us, you managed to clear a innocents name."

"You see, Kuroka and her sister are Nekoshou Yokai, their capable of using a art known as Senjutsu, which allows the user to absorb nature to boost their abilities." Ajuka explained.

"But if they absorb too much , they'll go berserk?" 

"Correct, that's what we thought happened to Kuroka when she killed her master, but now we know she did so to protect her sister." Sirzechs nodded.

"Speaking off... why does her sisters name feel....familiar?"

"You know her by another name, Koneko." Sirzechs explained.

"Koneko?!"

"After Kuroka went rouge, Koneko was nearly executed but i managed to prevent that pass her to Rias as her rook. But she as cast away everything about her old life, from her true name to her identity as a Nekoshou."

"I see..."  Y/n said before he felt a dark aura, looking on the back of his right hand,  he saw the symbol appear and one of it's prongs flashing purple.

"It looks like it's acting as a compass to a Zeroth dragon if their seal is weakened." Ajuka said.

"Then i better hurry." Y/n said as he spread his wings.

"Good luck N/n." Serafall said with a wink.

This caused slightly caught Y/n of guard, but he quickly shook it off and flew to where he sensed the aura. Soon he saw a large purple glowing symbol on the ground, raising from it was the Zeroth dragon.

"What power.... if i wasn't the wielder of my gears, i definitely would of be crushed under the pressure.." Y/n mumble. "Overlord, Zoa, any info?"

"This Zeroth dragon you see before you is known as the end of the world, Dust. He inherited the highest level of Gyze's negative mind. This made him unique among Zeroth Dragons, they say when he descended to the underworld, he banished all spirits except those of darkness attribute." Overlord explained.

"Be warned child, Dust can negate the powers of anything around him. Regardless if it's magic of any race, or sacred gears, no matter how powerful, even if it's a longinus." Zoa explained.

"Well isn't that just great? How am i supposed to even stand a chance then ?"

"I can help with that child, using my own aura, i can cancel out Dust's negation effects, though only temporary." Zoa said. "You have 5 minutes at most, make every second count."

Y/n didn't need to be told twice as he flew at Dust at fast speeds surrounded by fire, turning him into a flaming meteor. He struck Dust's back, causing a explosion and catching the Zeroth dragon off guard.

"How?!" Dust roared in pain, surprised someone attacked him, even more surprised that they could use their powers in his presence.

Not wasting any time, Y/n equipped his boosted gear and began to boost his power.

"Dragon shot!"

Y/n fired a concentrated blast of his magic and fire at Dust, the attack struck the Zeroth's dragons eyes, causing him to let out another roar of pain.

Dust began to fire concentrated blast of dark energy, causing Y/n to dodge and weave.

"Any ideas? I doubt my attacks will do much damage and his eyes are too small of a target, i won't get another lucky shot."

" I have, but i guarantee you won't like it one bit." Overlord said.

"Shoot! It doesn't look i have much choice and i'm running out of time!"

Overlord explained his plan, Y/n while surprised, decided to go though with it. He then dodged Dust's attacks as he flew at the Zeroth dragon while being surrounded by fire. He then flew in Dust's mouth, causing the Zeroth dragon to try and devour him. But the dragon soon roared in pain as, crimson fire escaped his mouth as Y/n rampaged inside, firing multiple dragons shots before gathering as much fire as he can before releasing it in a powerful burst.

Y/n escaped Dust's mouth as the Zeroth dragon fell to the ground in pain, he then saw the symbol appearing on the back of his right hand. Knowing what to do, holding out his hand, Dust began purple particles before being absorbed into palm, once Dust was fully absorbed, Y/n saw one of the prongs glowing purple along with the original green before the symbol faded away.

"I'm beat.... i barely have enough magic to keep my wings out."

Y/n then flew back to the satan's who has just finished discussing the situation with Kuroka, they took down her tittle as a stray devil and gave Y/n a folder with proof of her innocence to show to Koneko.

A few minutes later, Y/n was back at his mansion. He has been pacing back and forward for a few minutes.

"Let me guess...., you don't know how to break it to her?" Overlord asked despite knowing the answer.

"Exactly, she kept this a secret for so long. I don't know how'd she react to me "suddenly" knowing it, or to what happened."

"It's best to rip of that band aid quickly, the longer you stall, the worst it's going to get."

Y/n let out a long sigh before pulling out his phone, he then texted Rias to come to him room and call Koneko to come with her. As he waited, he heard a new voice in his head.

"To think i been resealed, inside of a devil no less."

Entering his mind, Y/n saw Dust with the other three dragons.

"So your the one Messiah spoke off? Interesting..."

"How are you this calm? If you inherited the highest level of Gyze's negative mind, i thought you be cursing me at the very least."

"I find you interesting, not only do you wield two powerful sacred gears, your also chosen by Messiah to hold us and your chosen by the lady of the lake to reforge the true Excalibur. So i'm more interested then annoyed." Dust said. "While irate you bested me in combat, you did earn my respect. Since i am sealed, i request a home in your mind."

Seeing Overlord nod, Y/n made a part of his mind a large land of everlasting night .

"My presence within you will grant you the purest form of darkness magic, and no,darkness magic is not solely used by evil nor is light magic solely used by good. It depends on the user."

"I can tell, seeing fallen angels still use light magic."

"Smart child, come to my home once your ready to learn." Dust said before he left for his new home

Once he woke to the real world, see saw Rias and Koneko enter his room.

 "Y/n, why did you call us ?" Rias asked.

Y/n sighed before handing the folder to Koneko, the rook began to read though it before she began to tremble , Y/n could't blame her, what she believed about her sister and past was a lie and she's now learning the truth.

After she was done reading, tears were falling from her eyes as her cat ears appeared. Y/n and Rias, who Y/n whispered the situation to while she was reading hugged and comforted her. They stayed like that for an hour.

Timeskip

The next day, both peerages were at Y/n's living room, there Koneko was seen on Y/n's lap and is bickering with Ravel.

"Get off him!" Ravel snapped.

"Make me fried chicken, this is my spot" Koneko deadpanned.

"F-fried chicken?! How dare you?! That's my king's lap your sitting on."

"He was with us first , deal with it."

Y/n chuckles as he tried to calm them down, at the corner of his eye, Y/n saw Clear wing talking with Odd eyes and Dark Rebellion, having decided to join her fellow dimension dragon as one of his familiars. Y/n could only wonder what the future holds.

Done and done, next time the ORC will meet up with a trio of exorcist about some business in Kouh and Y/n's mission of reforging the true Excalibur will truly begin. How will things go down? Read to find out.