In a beautiful Sunday morning, Y/n was currently walking around Kouh since he had some free time.  Holding to his arms was both Akeno and Yubelluna, both slightly glaring at the other queen while hugging Y/n's arm.

 How did it come to this? We'll need to backtrack a few hours

Flashback 

Y/n was currently in his room playing Crash bandicoot 4, it's about time in his PS5, trying to beat the level he's been stuck in for a while now.

"Come on, come on..." Y/n muttered as he pressed the buttons on the controller, but he mistimed a button press and got killed, sending him back to his last checkpoint. "No! Blast it!"

"You need to work on your reflexes." Overload said in his mind. "In game or in actual battle, one wrong move or slow reaction can and will cost you."

"Noted." Y/n said as he put the controller aside to stretch his limbs.

Y/n then heard a knock on his door. "Come in."

Akeno then entered. "Hey Y/n, do you have any free time later?"

"Yeah, why?"

"I realized that ever since joined us, we never got the chance to get to know each other, i would like to fix that."

"Now that you mentioned it, your right, sure."

"I'll be join you both." Yubelluna said as she appeared.

"Oh, And why should you? It's between me and my precious junior, i suggest you stay out of it." Akeno said, she sounds calm, but her eyes showed irritation towards the other queen.

"A queen should always be at their kings side, you know this."  Yubelluna shot back." And with what i heard about you, your the last one i'll leave him alone with."

Akeno's irritation only grew at that as her aura to leak out, Yubelluna let out her own aura in responds, but they soon stopped when Y/n got between them.

"E-easy there you two, lets all go together, my treat."

Both queens agreed, knowing arguing won't get them anywhere and it was better then nothing.

Flashback end

Now the three of them are at the arcade, Y/n was watching the queens play air hockey, he had his hands behind his back reading a memory erasing spell, knowing when devils compete, things can get out of of hand as magic is involved and the rules get thrown out of the window.

And sure enough, Akeno added magic to the puck as she hit it back to Yubelluna who did the same. The puck was knocked back and forward on the hockey table with unbelievable speeds, making it hard for most to track. It suddenly slowed to a stop.

"Looks like times up." Y/n said as he saw the timer at zero.

Luckily no one saw them use magic, most are astonished by the speed,others focused on something .... else.

After a few more games with the two tying with a score of two each, the three were at a cafe having something to eat.

"Y/n." Akeno said. Said pawn/king turned her way. "Ah~" She held up a spoon with ice cream to him. Blushing slightly, Y/n let Akeno feed him. She looks at him expectantly, knowing what she wants, he feeds her some of his.

Feeling Yubelluna's aura flare a little, Y/n fed some to her and she fed him after.  The three enjoyed their hangout until evening, once out of sight of any human, Akeno created a magic circle to teleport home.

"I had a good time Y/n." Akeno said with a smile. "Even though she came along." She thought as she sneaked a glance at Yubelluna.

"I had a good time too Akeno." Y/n said with a smile as well.

After Akeno teleported home, Y/n and Yubelluna was about to do the same, but suddenly Overload spoke to his partner.

"Partner, bad news!"

Sensing the panic in Overlord's voice startled him." What do you mean?"

"Do you remember what i told you about the Zeroth dragons?" Overlord asked. " I sense one near Kouh and it's seal is weakening and is close to breaking."

"Say what?! Which one?"

"The one known to many as Death Garden, Zoa."Overlord said. " The Zeroth Dragon which had absorbed the greatest number of spirits. The maintenance of its body required enormous amounts of mana, and it devoured mana from the atmosphere even after its incarnation. Leaving the nation it was created from nearly a wasteland.

"Yikes, but if what you say is true, we need to reseal it before anything happens."

"Easier said then done partner, it took many lives to help seal Messiah even one away, what do you think you alone can do?"

"I have a idea, Ddraig, can  you boost my strength to it's limit while we get to the seal?"

"I can, but mind if i ask why?" Ddraig asked.

"Let's just say, i feel a little reckless."

Y/n spread his wings and was ready to take off, but he was stopped by his queen who quickly grabbed his arm.

"Wait, i'm coming with you."

"It's too dangerous."

"As i said before, a queen must always be at their kings side, i'm going." Yubelluna said in a tone that left no room for argument.

"Very well..." 

Guided by Overload, they flew good distance from Kouh, they saw a large green glowing symbol on the ground, raising from it was the Zeroth dragon.

"This pressure is overwhelming..." Yubelluna could only say.

"Then we better hurry." Y/n said as he placed a hand on her shoulder.

"Transfer!"

Transferring his boost to Yubelluna, both of them fired a powerful blast of fire and magic.  Still weaken by the seal, the dragon could't react quickly enough and was struck on the back hard, causing it to roar in pain. 

"Who dares strike me!?" Zoa roared in anger.

Y/n then flew circles around the Zeroth dragon, leaving a trail of fire as he flew, trapping it in a wall of flames.

"Alright, how to reseal it?"

"We can't reseal her in her original seal as she destroyed it, and the method used before has been lost in time." Overlord explained.

"Great, now what?" Y/n grumbled.

"Use this power to seal the Zeroth dragon." A unknown female voice said in Y/n's mind.

Instinctively, Y/n held up his right arm towards Zoa, the symbol appeared on the back on his hand as the Zeroth dragon became green particles that was absorbed into his palm. Once Zoa was fully absorbed, Y/n saw one of the prongs glowing green before the symbol faded away.

"Who was..." 

"I believe that was Messiah." Overlord said. "It's the only explanation i can think off.

"All that effort to break free, only to be resealed inside a devil, how humiliating...." Someone grumbled in Y/n's mind.

"Don't tell me...." Y/n thought before entering his mind, there he saw Overlord and Ddraig along  with Zoa. 

"Despite my annoyance from once again being sealed, i will commend you for striking when the iron is hot, attacking me before i can absorb any mana." Zoa said. "However, i warn you, my brethren will not be as easy.

"I'm surprised your calm and not threatening me."

"I maybe sealed again, but i at least can interact with the outside world somewhat."  Zoa said. " In exchange for lending you my power, i request a place to call home within your mind."

Y/n looked at Overlord and Ddraig who nodded, concentrating, the area near them became a large forest that's big enough for Zoa.

"Having me in you will grant you access to nature magic, come to my home once your ready to learn. " Zoa said before she leaving for her new home.

"How am i going to explain this...?"

After returning home, Y/n informed Rias about what happened. After she reported it to her brother, he appointed Y/n to handle the Zeroth dragons should any of them break free from their seals.

As Y/n lied on his bed, Y/n could only wonder what the future holds.

Done and done, next time Y/n will spend time with the Gremony sisters and his mansion will be getting a few maids from  their brother, who could they be? Read to find out.