Issei's parents are killed by orders of Kokabiel and he is left all alone. As he is about to get killed by the people who killed his parents Ophis comes to save him. He learns that he is the great-grandson of the Vanishing Dragon Albion and coincidentally has his sacred gear Divine Dividing and the strongest Vritra sacred gear.
"And why would a Fallen Angel be sent with the intent to kill you?" Asked Sona.
"That's because I have a sacred gear and she was sent to get rid of me" He replied.
"And which sacred gear do you have?" Rias asked.
"I possess the sacred gear called the Prison of Ruin, the strongest of the Vritra sacred gears" He replied.
The Kings and peerages were dumbfounded to say the least. Issei had assumed they never heard of Prison of Ruin so he decided to show them.
Issei activated his sacred gear and they were taken back to see that it was an actual sacred gear.
[Hello Gremory and Sitri. I am the Black Prison Dragon, Vritra]
"I didn't know that there was a sacred gear which had the consciousness of Vritra" Said Sona. "I thought your soul was scattered"
[Only my powers were scattered and my soul was put into this sacred gear. Your pawn also has one of my sacred gears but we will discuss that later]
"I see now the question is, are you a threat to us?" Asked Sona
"As long as none of you get in the way of my plans I won't bother any of you" Replied Issei.
"I see thank you for your honesty" Said Rias "That would conclude this meeting you are all dismissed"
"I would like to talk to you Sitri-senpai before I leave"
Sona nods and they wait for the peerages to leave to continue the conversation.
"Now onto business. Sona, there is something that Vritra would like to discuss with you about"
[That is correct. Now young Sitri, I would like for you to hand over your pawn to us]
Sona raised an eyebrow at this request, shocked that he would ask of this. "And why would you want him Vritra?"
[Your pawn is too weak Sitri, he doesn't deserve a piece of me]
"Lets assume that I do give you him what's in it for me?" She asked.
[We would grant you any request, as long as we can fulfil it]
Sona thought hard about this request. If she were to give Saji to them they would owe her a favor. 'Maybe they can help Rias with her forced marriage!' She thought.
"Fine" She said. "I'll let you have his sacred gear, but i need a favor from you"
"And what exactly shall you want from us?" Issei asked.
"Become my pawn. I could use your strength for any future events" She stated.
[You have a deal Sitri]
'WHAT'
[Issei you are too strong for any of her remaining pieces] Vritra stated in his thoughts. [Trust me]
"Good. Now lets make you my pawn" She said.
Sona got Issei to lay down on the ground and placed her remaining 4 pawn pieces on his chest. 'Hopefully this is enough' She thought.
"In the name of Sona Sitri, I call to you, Issei Hyoudou, to be reborn as my devil servant. You my pawn, flow with the tide of the underworld, and live under my command"
Nothing. Nothing had happened. 'It seems that he is too strong for only 4 pawn pieces' Sona thought.
"It seems that I am too powerful to be reincarnated" Issei said. "Because of that I'll be willing to grant you 3 favors as long as they are within my power"
"Thank you" She said with a hint of sadness in her voice. "You should head back to class"
"I'll see you soon Sitri-senpai"
With that he left. Leaving Sona there thinking about what has happened.
'How powerful are you Issei Hyoudou?'
--------++++
'Hehe well that went better than expected now didn't it Vritra'
[Its almost worrisome how she easily agreed to hand over her pawn]
'So what? You said it yourself he's only a pawn. The guy's replaceable. Sitri-senpai can just get a new one'
(You don't understand Issei)
'What don't I understand'
[Although it may not be a crime, knowing that a servant is endanger and willingly do nothing about it is very taboo in devil society]
(If word gets out that the Sitri allowed a servant of hers to perish will result in her being looked down upon by all devils)
[And her family could legally remove her from the household to keep some respect in the underworld]
'So if she's allowing me to dispose of Saji...'
[There is something she needs from you that's so important]
(She's risking her entire future future on it)
'Just what did I get myself into?'
[Timeskip End of School]
The rest of the school day went fast for Issei as he was practically sleeping on his desk. It almost surprised him that no one had bothered him at all but that ended when the "Prince of Kuoh" had walked up to him.
"Hyoudou-san, my buchou would like to have a word with you" He said.
"Oh? Here I thought that our business was over when I came into your clubroom earlier" Issei said.
"There are other matters she would like to speak to you about without the presence of the Student Council"
"Very well. Lead the way"
On their way to the clubroom Issei noticed that the knight seemed to be interacting with him in a more defensive manner. He seemed as if he has guard up incase Issei had tried to do anything against him. Earlier in the day he acted more care free but now even his movement seems a bit, for a lack of a better word, forced.
The two made way to the door of clubroom but he stopped to look at Issei before speaking."I need to go serve a client but buchou and the rest will be inside waiting for you" He said before walking away.
'What could possibly go wrong"
[Don't jinx yourself]
Issei walked inside to see the short white-haired girl, who interestingly enough had the same aura as Kuroka albeit at a more suppressed level but still noticeable, and the Queen of Gremory.
"Ara ara a dragon has invaded" She said. "What is a defenseless maiden such as myself supposed to do now?"