Dream:

We can see a 7 years old Y/n who was running away scared and in tears, while a man and a woman were chasing him

Father: come here you brat!

Y/n: n-no! Please stop!!

Mother: you damn failure!!

She arrives and kicks your back, making you falling down

Father: very well

He picked you up brutally

Father: we're going to get rid of you, finally

But then

??: no leave him alone!!

A 18 years old girl with short hairs and four small bat-like wings on her head screams

Y/n: help me Lilith!!

Lilith: please leave my brother alone!!

She was crying

Mother: shut up!!

She punched Lilith making her falling down

Y/n: LILITH!!!!

The time then skipped. Showing the stage of Sabaody's auction house, where the seven years old Y/n was with a bomb collar, handcuffs and he was crying. While the announcer was screaming "AND THIS WAS SOLD!"

Those who bought you were celestial dragons

The time skipped again, to when Y/n was chained to a stone naked while the celestial dragons were marking him with the nobles symbol

Y/n: AAAAAAARGH!!!!!!!

You woke up

You looked was sweating and you was scared

Ulti: hey! Hey! Calm down!

Hearing her voice made you calm down. You looked up, and you saw Ulti's face. However, she removed her mask, something she doesn't usually does

(Credits: idk but this pic is not mine)

Y/n: a-aneki...?

Ulti: yes it's me-

You stood up from her lap and gave her a hug, while you was almost crying again

Ulti: shh it's ok... I'm here

While you was hugging her, you looked at the music box. It was closed. You understood she closed it while you fainted. After your outburst at Rias, you only remembered to be really angry, and when you was conscient again you remembered the trees destroyed and then, climbing on a tree and opening the music box

You broke the hug and you looked at her in her eyes. She had sad eyes perhaps what you did affected her

Ulti: please... don't do that anymore!

You felt guilty. After all, it wasn't her fault, but the bad memories flooding back just fueled the outburst

Y/n: thanks to you... I'm feeling better... Ulti-nee chan

She had a small shock in hearing how you called her. The last time you did you was 13. She had a small blush

Ulti: let's go back. Pay-tan it's with the others

Y/n: alrig-

You heard a heart beat

Y/n: no...

Ulti: Y/n-tan...?

You held your head with your hands

Y/n: stop it... stop it... stop it!!!!

The sclera of your eyes became black again, and your hands became dark and sharped claws

Y/n(?): follow me

Ulti: who are you?! What have you done  to my brother!!!

Y/n(?): it doesn't matter now. Follow me

Even if she was confused she followed "you"

Meanwhile:

The man, now knowed as Hades introduced himself. Everyone were shocked in hearing his name

Rias: H-Hades...? The greek god of the Netherworld?!

Kokabiel was visibly scared but he decided to not showing him

Kokabiel: I-I don't care who are you!

Hades: I'm here cause there is a person I need to meet... but he is not here. However, I can't ignore what's happening

Kokabiel: you know what?! No matter if you are a God or no, I'll kill you!

Hades: I'd suggest you to don't do that. Just, give up and you will live

Kokabiel: screw you!!!

He created a lot of light spears

The others were just shocked

Kokabiel then smirked

Kokabiel: if I kill a Chief God... I'll start a huge war. It was a mistake for you to come here, Hades!

He threw him the spears. Hades simply thrusted forward his bident and destroyed all the light spears. Like some low class attacks can hurt big bro- I meant, Hades

Hades: I guess it can't be helped

He jumped very high until he was at the same height of Kokabiel and held his bident from the extreme point of the hilt, before attacking

Hades: Persephone Titan!

The attack striked Kokabiel, breaking a few bones of him and cutting 6 of his wings

Kokabiel: AAAAAARGH!!!!!!

Hades: if you give up, I'll spare you

But then

*crack* *boom*

The barrier was broken

Sona: w-what?! How was the barrier broken?!

But then, everyone except for Hades started to feel really scared, as a creepy tune started to play

Issei: w-what is this?!

Akeno: a-ara ara~

Hades: huh?

Tsubaki: w-who are you?!

Saji: what's this creepy song that's playing?

Even Koneko, who was mostly calm and collected was scared, same for Page One

Then, someone started to sing the song

??: London Bridge is falling down... falling down... falling down...

Issei: this song?

Xenovia: London Bridge is falling down?

??: London Bridge is falling down... my fair lady...

The figure appeared from the darkness, revealing it was you

Rias: Y-Y/n?

Page One: little brother?

However, you was different, your voice was deeper, and your hands were dark and sharped claws

Y/n(?): Silver and Gold will be stolen away... stolen away... stolen away... Silver and Gold will be stolen away... My fair lady... Silver and Gold will be stolen away... stolen away... stolen away... Silver and Gold will be stolen away... My fair lady...

Kokabiel: who are you?!

Y/n(?): Set a man to watch all night... watch all night... watch all night... set a man to watch all night... my... fair... lady...

(Sorry for to those who expected him to be Jack)

Kokabiel: DID YOU HEARD ME?! I AM TALKING TO YOU!!!!

Y/n(?): I'm not the boy you call Y/n... and why should I speak with someone who can't reach me...

Rias: w-who are you?!

Y/n(?): my name... is Satan... the creator of Hell... I am this boy... this boy is me... we are one and the same...

Hades: looks like Zeus was right

Satan: Hades... the King of Helheim... why are you here?

Hades: for that boy

Satan: oh... him...? I'll let him talk to you soon...

Satan then rushed Kokabiel who tried to escape and almost ripped his heart off

Kokabiel: AAAAAARGH!!!!!!!

Satan: who is the low-class being?

Kokabiel fell down. But then on the sky appeared a man with a silver armor

Rias: White Dragon Emperor!

The man stood there

WDE: greetings, Rias Gremory. Thank you for taking care of the annoying part of Kokabiel, now if you don't mind I'll take him from your hand

Issei was suddenly angry and activated his Sacred Gear

Ddraig: are you going to ignore me Albion?

Albion: Ddraig, I see you finally found a host

Ddraig: ...

Albion: there we go. Vali, let's come back to the HQ

Vali took Kokabiel and flied away

You took conscience again and you was confused

Y/n: uhhh.... what happened...?

Page One and Ulti ran to you

Page One: Y/n are you ok?

Ulti: what is this story of Satan?!

Y/n: it's a long story

??: hey

You turned around and you saw Hades walking to you

Hades: hey boy

Y/n: uh... who are you sir?

Hades: my name is Hades

Y/n: Hades...?- wait- like the greek god?!

Hades: I am Hades, the king of Helheim and the greek god of death

Y/n: w-why is a god here?

Hades: I was looking for you

Y/n: me?!

Hades: exatly. You have to come with me

Ulti: why?!

Hades: it's something personal, but it won't last long

Page One: aneki, let's do what he said

Ulti:, uff fine

The ORC and Sona's peerage were confused

Y/n: alright, I'll come