3rd person pov

The Devil fired  blasts at Aizen to little effect before Grimmjow charged towards him. Aizen blocked her attack causing a shock wave.

Grimmjow: Damn you.

Aizen chuckled before  knocking her aside when Starrk appeared infront of him. As Starrk fired a cero Aizen appeared behind him. Aizen prepared to cut Starrk down but was met with a punch from Mila Rose. The other Members Fraccion continued their assault on Aizen; not giving any room. As they fired ceros at Aizen the mastermind stopped it with Danku. Nelliel  used Sonido to appear behind Aizen then fired a Gran rey cero with Harribel. Having engulfed Aizen in an explosion they quickly entered their release forms.

Nelliel: Declare Gazuma!

Aizen: I'm impressed that Kisuke would assist you Nelliel.

Nelliel: We will do whatever it takes to end you Aizen! For all the Chaos you've caused it all ends here!

Aizen: You really shouldn't say things like that; It makes you look weak.

???: Then how about saying this?

Nelliel jumped back when Aizen saw Kisuke behind him.

Kisuke: Scream Benihime! 

Kisuke swung his blade unleashing a red blast of energy at Aizen. Aizen having been launched into the air was then met with two more attacks.

Nemu: Permission to use my full power was granted by Master Mayuri; now die.

Momo: Snap Tobiume!

The two female Soul Reapers unleashed their attacks on Aizen sending him crashing into the ground.  Sajin unleashed his Bankai  before swinging it's blade down on Aizen.  Aizen flew above everyone then chuckled.

Aizen: All of you are no match for me. I've said it before no matter how many of you attack me;nothing will change.

Isabella: Shut the hell up none of us care about that! So what if we aren't as strong as you; no matter what we won't give up!

Riser: Riser agrees  we will never surrender to trash like you not now not ever!

Yamamoto: It is our job to maintain peace between the souls of all beings. Your presence only causes chaos Sosuke Aizen! You are a threat not only to the world of the living but to all life in this world.

Aizen: I'm  only doing what  all creatures should strive for.

Sirzechs: What kind of sick world do you live in where everyone should kill for power?!

Aizen: I'm not searching for power; what I want it evolution. To become something greater than all others.

Micheal: Just how does destroying Heaven and Hell help you achieve that goal?

Aizen: In order to awaken the sleeping power inside that boy; Y/n L/n.

Everyone looked at Aizen in shock at the mastermind's words.

Byakuya: Explain what you mean about Y/n now.

Aizen: That boy is not an ordinary  Soul Reaper or even a Visored. Deep inside him is a power that even greater than Soul King himself. Y/n L/n has the power to observe our very reality and change it.

Rias: That can't be.

Aizen: I'm afraid it's all true Crimson haired princess of ruin.

Kisuke: So that was your reason all along.

Riser: YOU BASTARD I'LL INCINERATE YOU BEFORE YOU CAN LAY A FINGER ON Y/N! RISER WILL NOT ALLOW YOU TO HURT THE MAN HE SEES AS HIS BROTHER!!

Riser unleashed a powerful flame at Aizen before everyone continued their attacks.

(Meanwhile with Y/n)

Y/n blocked a strike from Tensa Zangetsu  before seeing his Hollow behind him.  The Hollow went to slash him only for Y/n to jump above them.

Y/n(Hollow)  Your a damn fool King if you think we are gonna let you kill yourself like that!Mugetsu will strip you of everything you have!

Tensa: We won't stand by and watch you destroy the one thing we desire to protect; we won't let you destroy yourself.

Y/n: If I can beat Aizen then my life doesn't matter.  I refuse to allow everyone to continue to suffer by Aizen's hands anymore! 

Tensa: Does their lives matter that much to you? That your willing to toss everything aside for their sake?!

Y/n: Damn straight I will.

Tensa and Y/n's inner Hollow stood in disbelief before looking down.

Tensa: If your willing to go this far..

Y/n(Hollow)  Then so be it!

The two's bodies began to glow causing Y/n to cover his eyes. When the light vanished Y/n stared at their new form.

Tensa:  Come at us

Timeskip brought to you by these

3rd person pov

7 minutes later Aizen stood staring at the beaten Races with his spirit energy flowing from his body.

Irina: SIR MICHEAL PLEASE HOLD ON!

Aizen: I'll end this meaningless battle now.

Aizen fired a blast towards them causing Irina to brace herself. Before Aizen's attack could hit something suddenly slammed infront of them stopping it.

Irina: What?

Irina stared in awe at the man standing infront of her. The man turned to reveal Y/n's face staring back at her.

Y/n: Irina I want you and anyone who can stand to take the injured.Get them out of here as fast as you can; i'll handle things here.

Aizen: So this is what you have chosen? You have chosen to reject your power in place of evolution? I must say i'm surprised Y/n L/n, you truly are interesting.

Y/n: All of the suffering you've caused ends...Aizen. With this blade I'll pass judgement for everything you've done.

Aizen smirked then raised  his blade and aimed it at Y/n.

Aizen: Let's see about that shall we?

 Y/n flashstepped infront of Aizen before swinging his blade. Barely managing to block ;Aizen was sent flying far away.

Y/n: I'm counting on you Irina.

Without saying another word Y/n vanished towards Aizen. Aizen stopped himself before swing his sword at Y/n causing the boy to block. As he did everything around them shattered. Y/n went to impale Aizen before  swinging behind himself. Y/n glared at the sight of Aizen who stood behind him.

Y/n: Your tricks aren't gonna work on me Aizen..

Aizen:(mind) He was able to see through Kyoka Suigetsu's illusions? Well no matter I don't need that alone.

Aizen slashed at Y/n who block with ease.  With every strike made the others watched as everything around the two blew apart.

Rias:(mind) Your so strong it's like your a different person. The way your eyes looked at us; It's like staring at someone new. 

Sona walked up to Rias and placed her hand on the Gremory's shoulder.

Sona: Rias we need to go now. Y/n is counting on us to help the others. Let's not let him down alright?

Rias:*Nods*  Yeah let's go. *mentally*  Y/n deep down your still the man I love so please, I beg you; Free us all!

Rias and Sona helped Irina take the injured before staring back at Y/n one last time. After leaving Y/n and Aizen's battle continued to tear everything apart. Aizen fired a Kido spell at Y/n causing the boy block with the side of his blade. Y/n  unleashed a blast at Aizen;managing to cut off his arm. Aizen stared at Y/n in surprise before sending Y/n back.

Aizen: Your strength is amazing just like Kurosaki's was that day. Your  eyes are different since they were before. Now I can see power behind them but for how long?

Y/n: How long do you plan to keep up these monologues of yours? I came to fight not listen to your villain speeches. 

Aizen smirked before  appearing behind Y/n with insane speed.  Aizen fired a  blast at Y/n causing the boy to stop it with his bare hand. Not giving Y/n anytime to react Aizen slashed Y/n's arm. Y/n didn't flinch but only swung his blade with his other hand. Aizen jumped back then raised his hand to the sky.

Aizen:  Seeping crest of turbidity. Arrogant vessel of lunacy. Boil forth and deny.Grow numb and flicker. Disrupt sleep. Crawling queen of iron. Eternally self-destructing doll of mud. Unite. Repulse. Fill  with soul and know your own powerlessness. Hado # 90 Kurohitsugi!

Y/n watched as a black coffin made of spirit energy formed around him. Y/n did nothing only staring at Aizen before sighing. When the Kido spell had finished around Y/n Aizen stood his arm now reattached.

Aizen: What will you do now Y/n L/n?

A second later Y/n spiritual pressure grew shattering the spell with ease. Y/n appeared infront of Aizen using flashstep. Y/n stared at Y/n as his blade covered itself in black spirit energy.

Y/n: I won't bow to you Aizen. No matter what i'm winning even if; I have to turn everything to black.

Aizen:(mind)So that's what he's planning.

Y/n: Mugetsu....

Y/n swung his blade unleashing a massive wave of his spirit energy. The others back in the world of the living watched in utter disbelief as Y/n turned the sky black.

Isabella: What...the hell did Y/n just do?

Ichigo: NO WE NEED TO GO BACK NOW!

Isshin grabbed Ichigo  causing the girl to struggle.

Ichigo: DAMMIT DAD LET GO HE'S GONNA BE POWERLESS!  AIZEN WILL KILL HIM IF WE DON'T DO SOMETHING!

Isshin: Ichigo calm down and look closer.

Ichigo  looked back seeing Aizen standing damaged. Y/n spirit energy vanished from the sky then what they saw next; None of them were prepared for.

To be continued