???: The little sister of Straw Hat Y/n... I'm going to enjoy torturing you and your peerage.

Right now, Rias, Asia, and Issei are looking at the man with strings impaling Issei with confusion in their eyes.

Rias: W-Who are you?

Doflamingo: You can call me Donquixote Doflamingo.

Riser: How do you like this Rias? Riser has brought an incredibly strong piece into the game.

Doflamingo then turns to Riser and glares at him.

Doflamingo: You remember our arrangement, I get to torture the little sister of Straw Hat Y/n and you get to have your way with her after we are done.

Riser: Of course my friend, Riser never goes back on his deals.

Issei: You bastards! I'll kill you both

Issei then charges at Doflamingo and Riser, only to be kicked to the ground hard by Doflamingo.

Issei: GAH!

Riser: How weak!

Doflamingo: This is the Red Dragon Emperor? How pathetic...

Issei: Shut your mouth you damn bastard!

He attempts to punch Doflamingo, but he catches it and twists Issei's arm and punches him hard in the gut sending him to the ground.

Doflamingo: Tsch.

He then looks towards Rias.

Doflamingo: Let's see how you face looks when I crush the head of your pathetic pawn. He's starting to annoy me.

Asia: Issei!

Rias: NO!

Doflamingo: Don't worry, I'll get to torturing you two later.

Issei: D-Damn, this guy is no j-joke. I'm really going to die here. I couldn't even land a hit on him... I'm sorry Rias, Y/n-Sensei.

Doflamingo then begins to walk towards Issei.

Doflamingo: While I might not be able to kill you right now, I can at least stop your breath.

He then proceeds to raise his foot above Issei's throat while laughing.

Issei: Tsch.

Time begins to slow down as Rias and Asia look on in terror.

Rias/Asia: ISSEI!!!!!!

Rias then feels something placed on her head....

She looks up to see her big brother Y/n standing there, an angry look on his face.

Rias: Y-Y/n?

Y/n: Say the words Rias and I'll do what needs to be done.

Rias then begins to cry.

Rias: BIG BROTHER, PLEASE SAVE ME!

Y/n then takes a deep breath and raises his hands towards the sky.

Y/n: OF COURSE I WILL!

He then disappears.

RIght before Doflamingo's foot hits Issei's throat, he screams out

Issei: DAMN!

Suddenly....

Doflamingo's foot is stopped in place by Y/n, who looks up at him.

Issei: Damn... Y/n-sensei.

Y/n then turns to Rias and Asia.

Y/n: Rias.... Asia.... You two need to go! I'll deal with these two.

Rias: Right! Come on Asia.

Asia: B-But Issei...

Issei: G-Go! I'll be fine!

Riser: I won't let you leave!

He begins to charge up a massive fireball.

Riser: THIS WILL SHOW YOU NOT TO DEFY RISER, MY BELOVED RIAS!

He throws the fireball at Rias and Asia and they close there eyes in fear. Just as the ball is about to hit them, it is cut in half. Infront of them stands Trafalgar with his sword out. Doflamingo glares at him.

Doflamingo: YOU!

Law: Nice to see you to Doflamingo, I would stay here to watch you get your ass kicked by my captain, but I believe I have other orders.

Y/n: Nice of you to join us Traffy, can you help them get out of here?

Law: You got it Captain, make sure to kick his ass for me.

Y/n glares at Doflamingo.

Y/n: Don't worry I plan to.

Law then grabs Rias and Asia and teleports away, but not before getting Issei out from underneath Doflamingo and Y/n with Shambles.

Doflamingo: Damn that Law, now I'm really starting to get pissed!

Y/n: Same here! Now take this!

Y/n kicks Doflamingo away causing him to skid next to Riser while Y/n skids next to a still downed Issei.

Y/n: You alright Issei?

Issei: I will be. Just gotta use this.

Issei then slowly pulls out a bottle and Riser's eyes widened.

Riser: Where did you get that bottle?!

Issei: Heh, I stole it off your queen when I knocked her ass out with one punch.

Y/n: The Phenex Tears said to heal any wound, nice job Issei.

Issei then opens the bottle and pours it on himself, he is engulfed in a golden light before standing up and stretching.

Issei: Damn I feel like a million bucks.

He then looks at Y/n with a smirk.

Issei: Sensei, will you join me in this fight?

Y/n begins to laugh.

Y/n: Shishishishi, sure thing Issei. Let's kick their asses.

Riser and Doflamingo glare at them.

Riser: Very well.

Doflamingo: Since I don't get to torture your sister, I'll just torture you instead!

https://youtu.be/y05e1zJ1U8Q

Y/n walks up to Doflamingo and the glare at each other for a second, before they both swing their legs at each other and clash, both Armament Haki and Conqueror's Haki.

Issei and Riser look on.

Issei: W-Woah, this is the power of the Conqeuror's Haki clashing, it's incredible.

Issei then senses an attack coming towards him and dodges.

Riser: Pay attention to your fight with Riser boy! I'm going to make you suffer!

Issei: I'll show you why I'm the Red Dragon Emperor. Ddraig are you ready?

The gem on Issei's gauntlet then glows green and speaks.

Ddraig: Of course I am partner, normally I would have to ask you to sacrafice a part of yourself in order to achieve this form, but now your power enough is fine.

Issei: Then let's do it! PROMOTION: QUEEN!

Issei's aura then begins to flare up like a raging inferno.

Ddraig: WELSH DRAGON BALANCE BREAKER!

Issei then begins to gain a set of red armor covered in green gems, with red dragon wings popping out of the back.

Issei/Ddraig: BALANCE BREAKER BOOSTED GEAR, SCALE MAIL!!

(Oh yeah this version of Issei already has Balance Breaker, that training he did was so brutal I won't even ever write about it, he nearly died over 150 times, thank god for Chopper and Asia's godlike healing abilities)

Riser looks on and gives a smirk and chuckles.

Riser: You really think a silly set of armor is going to beat me.

But on the inside...

Riser: This energy, it exceeds mine, but no matter, I can just regenerate until his transformation runs out.

Meanwhile with Y/n and Doflamingo, the two engage in a clash of Armament Haki infused punches. The two punch each other so hard they go skidding back. Y/n then begins to charge up an attack using Gear Second.

Y/n: GOMU GOMU NO

He then rushes towards Doflamingo at an incredible speed, his fist looking like it's on fire. He then sends his fist foward punching Doflamingo so hard, fire emerges from the other side of his body, causing Doflamingo to cough up blood.

Y/n: RED HAWK!

Doflamingo: Damn it!

He goes rolling across the ground before stopping.

Issei/Ddraig: BALANCE BREAKER BOOSTED GEAR, SCALE MAIL!!

The two look over to see Issei turning into his Balance Breaker and Y/n smirks while Doflamingo growls.

Doflamingo: So that Red Dragon was holding back...

Y/n: Shishishi, that's my student for ya, now that he's shown off his transformation, I can show off mine!

Doflamingo: Oh, this is getting interesting now.

Y/n coats his arms in Haki before biting into his forearm, he then begins to blow air into his body. He then is covered in a lot of smoke from the pressure.

Y/n: KIN'NIKU FUSEN!

Doflamingo: What is he doing, his haki is rising fast!

Once the smoke clears, Y/n is now in a new form. His proportions have become warped, and his body becomes much larger in size, with his arms, upper torso, and legs coated in Armament Haki. He is also bouncing in place.

Y/n: GEAR FOURTH!

Y/n: BOUNDMAN!

Doflamingo: What the hell is this?! WHAT KIND OF JOKE IS THIS?! TAKE THIS MORE SERIOSULY!

Y/n: I am serious!

Y/n then charges towards Doflamingo while compressing his fist.

Y/n: GOMU GOMU NO

Y/n: KONG GUN!

He then punches Doflamingo, who tries to block, but he just ends up going flying away into the school courtyard.

Doflamingo: Damn... He broke through my defenses.

Y/n then begins to fly towards him as Doflamingo gets up and looks at him.

Doflamingo: He's flying using the elastic force!

He then charges up an attack and fires it at Y/n

Doflamingo: OVERHEAT!

Y/n dodges and disappears and reappears above Doflamingo.

Y/n: GOMU GOMU NO

Doflamingo: When did he-

Y/n: RHINO SCHNEIDER!

He then kicks Doflamingo in the face sending him flying into a nearby building.

Doflamingo steps out from building and flies into the air.

Doflamingo: He's alot faster and stronger then I anticpated.

Y/n then flies towards Doflamingo who attemps to hit him with a series of strings, Y/n however just dodges them while still advancing towards Doflamingo. Once Y/n gets close, Doflamingo disappears and reappears trying to kick Y/n in the torso. Only for the kick to bounce off of the torso.

Doflamingo: Armored, but still rubbery?

Y/n: A crappy attack like that...

Doflaimngo: Huh?

Y/n then flexes sending Doflamingo away.

Y/n: WON'T WORK ON ME!

Doflamingo: Damn it!

Y/n then looks at Doflamingo

Y/n: You're no match for me in Gear Fourth!

Doflamingo: Damn it Straw Hat! Stop messing with me!

Y/n then proceeds to charge up another punch.

Y/n: I'm going to make you pay for threatning my family and my student!

Doflamingo: Very well, let's end this then!

(Meanwhile with Issei and Riser)

Issei and Riser rush towards each other trading blows. Issei was dodging and knocking away the fireballs Riser attempted to throw at him.

Riser: COme on boy, is this truly your best? All you're doing is dodging Riser's attacks.

Issei: The best offense is a good defense ya know!

He continuted to dodge Riser's attacks, he then boosted and and blitzed towards Riser, he then delivered a massive kick to Riser's side.

Issei: WELSH DRAGON TAIL!

Issei then kicked Riser into one buildings. He landed and immediately charged towardfss Riser

Issei: WELSH DRAGON CLAW!

Riser managed to dodge flying into the air, causing Issei to hit a building, easily destroying a good chunk of it.

Issei: What's wrong KFC? I thought you wanted to play offense, this seems like defense to me.

Riser glared at Issei and launched a fireball barrage at Issei and began to dodge them all. 

Issei: This power is incredible... Thanks Ddraig.

Ddraig: Of course partner, but be careful, the more haki you use in the form, the more the time limit will be used up.

Issei: How much time do I have left?

Ddraig: Enough to finish the fight.

Issei was then hit with a massive barrage of fireballs, causing a massive amount of smoke to surrounded him. Riser eventually stopped and looked at the ground smirking.

Riser: It appears that Riser is the victor of this fight.

Issei: LIKE HELL YOU ARE!

Riser looked at the smoke cloud shocked.

Riser: WHAT?!

Ddraig: Boost x10!

Issei then sped out of the smoke cloud and appeared directly in front of riser and delivered a massive punch to Riser's gut sending him flying away and coughing up blood. Issei then sped back towards him as he recovered and Riser and Issei began to trade blows with Riser's defense beginning to falter.

Issei: I can tell you are getting tired KFC, just give up, Rias will never be yours!

Riser: Shut it boy, after I deal with you, I'll deal with that L/n-trash and get my sister back from him!

Issei: Like hell you'll get past me!

Riser: HOW CAN YOU NOT UNDERSTAND THAT THIS ENTIRE ENGAGEMENT IS IMPORTANT TO THE FUTURE OF ALL THE DEVILS! A GOOD FOR NOTHING LOW CLASS DEVIL LIKE YOU HAS NO BUSINESS GETTING INVOLVED!!!

Issei: I DON'T GIVE TWO DAMNS ABOUT ANY OF THAT!

https://youtu.be/sosj7fH1uBU

Issei's aura then began to flare up, Riser attempted to fire more attacks at Issei, but he just easily swatted them away.

Issei: I don't care about your marraige, I don't care about the future of any other devils except for those I care about.

Issei then began to charge a massive red/green flame in each of his hands.

Issei: RIAS GREMORY ISN'T YOUR PROPERTY! SHE DOESN'T BELONG TO ANYONE!

Riser also proceeded to summon a giant fireball.

Riser: I'LL END YOU BOY!

Meanwhile Y/n was fighting Doflamingo, who was using the surrounded environment which he had turn into strings to launch at Y/n, who was dodging them.

Y/n: I'm ending this fight with this very next attack!

Doflamingo: Very well.

Doflamingo then proceeded to create a giant spiderweb of strings in front of him, while sixteen haki infused strings stood next to him.

Y/n then proceeded to bite into his forearm while charging up a Kong Gun, causing the attack to grow bigger and bigger.

Y/n: DOFLAMINGO!

Doflamingo: Straw Hat!

The two then launched their attacks at each other, while Issei and Riser did the same.

Doflamingo: GOD THREAD!

Riser: Phenex Destruction Sphere!

Y/n: GOMU GOMU NO

Issei: WELSH DRAGON!

Y/n/Issei: KING KONG GUN/GIGANTIC BURST!

Y/n threw his giant punch at Doflamingo, who was helpless to stop it as he was sent soaring into the ground, causing it to split in half and uproot, he then proceeded to fall down the crack made in the ground and into the void, disappearing in a purple light.

Meanwhile Issei fired his blast at Riser, who much like Doflamingo was easily overwhelmed by the Dragon Emperor's attack and screamed in pain, once both attacks were finished, Issei and Y/n landed next to each other, both back in their base forms, before fist bumping each other.

Issei: Thanks for the training Sensei, there was no way I could have won the first without the guidance of you and your peerage.

Y/n: Don't self yourself short Issei, you did this with your own power, you took the Haki I gave you and made it your own, I couldn't be more proud.

Rias: Issei! Y/n!

Issei and Y/n look over to see Rias and her peerage, followed by Boa and Grayfia walking towards them, well the rest were walking towards them, Rias was sprinting towards them, she then tackled Issei in a hug.

Rias: Thank you two so much! You have no idea how happy I am.

Issei blushed and gave a small chuckle.

Issei: It was nothing, I said I would do anything to protect you and I meant it.

Rias then surprised everyone and kissed Issei on the lips. He eventually melted into the kiss, once she was finished, Issei was engulfed in a red/green light, once the Red/Green light died down, everyone was shocked to see...

Issei looked completly different.

Issei: What's everyone staring at.

Ddraig: It seems as if your body went through it's own Balance Breaker.

Issei: Huh?

He then quickly ran to a nearby body of water and looked into it.

Issei: Holy crap, I look good.

Rias/Asia: I-I-I...

Akeno: It seems those two are speechless.

Koneko: Huh, he looks more mature now.

Issei: This is gonna be hard to explain to my parents...

Boa: I'm sure a little bit of memory magic can fix all of this.

Grayfia: Anyway, Y/n, your elder brother would like to speak with you alone.

Y/n: Oh yeah sure, hey I hate to run guys but-

He is then hugged by Rias.

Rias: Thank you so much Big Brother, for saving me.

Y/n then hugged back smiling.

Y/n: Anytime sis.

He then took the Straw Hat off of her head.

Y/n: Can't leave without this, thanks for keeping it safe. Boa, I trust you can get home by yourself?

Boa: I'll let the rest of the peerage know what happened.

Y/n: Cool, see ya.

Y/n then teleported away and appeared in an office in front of a man with red hair.

Y/n: So... Whatcha wanna talk about Zechs?

Sirzechs: I want to thank you for saving our sister, but I also want to apologize for letting a criminal such as Doflamingo make his way into our sisters rating game.

Y/n: I'm still wondering how Riser found out about him.

Sirzechs: We have a spy in the Devil Socicety, working with the Kaos Brigade in order to bring in those you've faced before when you went on that journey all those years ago.

Y/n: So someone is breaking people out of Impel Down?

Sirzechs: It would seem, but as of right now we've increased security at the prison and have had Doflamingo teleported back into it.

Y/n: Good, so is that all youi wanted to talk to me about.

Sirzechs: There is one more thing, we have found our third Yonko Maou.

Y/n: Oh, who is it?

???: It's me Straw Hat.

Y/n freezes in place and slowly turns around. He is met with a girl with scarlet hair and wearing a suit of armor.

Y/n: E-Erza?!

Erza: Are you really that surprised?

Y/n: I mean yeah? I thought your dad Mihawk was one of the top choices for the Yonko Maou.

Erza: He was, but he declined, he said he didn't want to be in a position of power again, so he nominated me for the position. He did train me and you after all, I would say I'm on equal par with you when it comes to our sword skills.

Y/n: Eh? Are you trying to go for The Underworld's Greatest Swordsman?!

Erza: Of course I am, As Mihawk's Daughter, it's only right I inherit his title!

Y/n: Ah hell nah, that title is mine!

Erza: Bring it on Straw Hat!

Y/n: Let's go! Come on Enma!

Erza: Re-quip-

The two are then interuppted by Sirzechs chuckling behind them.

Y/n/Erza: What's so funny?

Sirzechs: There's also one more important piece of information, the both of you are going to be attending Kuoh Academy, together.

Erza: ....

Y/n: ....

Erza/Y/n: EHHHHHHHHHHHH?!?!

(That's right Erza Scarlet daughter of Mihawk and Irene Belserion is the newest Yonko Maou, which means that characters from Fairy Tail will be added to this story soon, the first Arc focused on Y/n's Luffy Side, the next arc or the Kokabiel Arc will focus on Y/n's Zoro Side since the arc involved swords, it's fitting, look forward to those chapters coming soon.)