You were sitting in class with your teacher talking about how to survive against Grimm and Stray Devils and how to combat them,

Teacher: Now you see, I'm sure Rias and her crew know this, but when a devil kills it betrays it's owner it will roam around Killing or Eating any defenceless humans in sight.

Issei: Yeah! That's right! I remember fighting my first stray devil!

Koneko: Don't remind me...

Bakugo: Who cares! I'll blow them away!

Everyone from class 1-a began to either laugh, face palm, or both. After class ended you were finishing Gathering your things when you saw Rias walking towards you, you quickly grabbed your stuff and made a run for it to your next class.

Rias: Wait! *Sigh*...I won't give up on it!

Kaminari: Mission Failed! We'll get em next time!

Issei motioned Kaminari to go away before putting his hand on Rias' shoulder with a surprising warming smile.

Issei: Don't worry, it won't be long until he joins us!

Eventually Lunch came around, you were sitting with Yang, Kirishima and Surprisingly Todoroki and Lie.

Todoroki: So what exactly is your quirk, L/N?

Lie: That's what I wanted to know as well, that's quite the semblance you've got there.

Y/N: Well, Like I've said multiple times before, it's not a Quirk, Semblance, Or Sacred Gear, It's just the power of my race!

Kirishima: Your race?

You nodded and smiled before explaining.

Y/N: The thing is, I'm not Human, I'm a saiyan, Saiyans have the power to grow stronger each time they fight, that's how I'm so strong!

Yang: You're not human?!

You shook you head before you heard a stomp behind you.

???: Hey L/N!

You looked behind you to see none other than Issei who was staring you down with a cocky glare.

Y/N: You again? How many times am I gonna have to deal with you guys?!

You got up from your seat and faced Issei.

Y/N: What do you want?

Issei: Heh, FIGHT ME L/N!

Rias: What?!

Koneko: Issei What are you doing?! Stop!

Y/N: I accept...

Everyone was surprised by your acceptance to Issei's challenge.

Issei: If I win, You have to join us!

Y/N: I still accept...There's clearly no risks if I'm up against you...

Issei: What'd you say you bastard?!

He activated the third form of his sacred gear and swung his fist at you, you ducked and glared at him.

Y/N: I said that there's no risks if I'm against you...

You then smashed your fist into his stomach before launching up through the roof with a Ki blast, you powered up before soaring after him.

Y/N: What a waste of energy...

You appeared above him and elbowed him to the ground making an explosion of dust and dirt. You looked down upon Issei who was still engulfed in a dust cloud

BOOST!

Suddenly Issei leaped out of the Smoke as you descended to the ground, Issei charged at you again and swung at you, you once again ducked and kicked him away.

Y/N: His Power is slowly multiplying...?

Issei got up from the ground and glared at you in frustration and rage.

Issei: I'm gonna beat you to the ground so damn hard!! OVER BOOSTER!!

Suddenly his red gauntlet began to glow, soon it began to emit a bright red light,

OVER BOOSTER!!!

Suddenly a bunch of red armor pieces appeared around Issei and began to attach to him, soon he was fully covered in crimson red armor.

Issei: BALANCE BREAKER: SCALE MAIL!

Y/N: What kind of power is that?

Ddraig: Issei there's something strange about him!

Issei: Huh? What do you mean?

Ddraig: I sense a power in him that's Very Strong!

Issei: What?!

You looked at your hands in confusion before realizing what he meant.

Y/N: Oh! You mean my transformations!

Issei: Enough talk! Fight me!

Issei rushed you with a series of swift punches and kicks, he was much faster and stronger than earlier, you had to block.

Y/N: He transformed...yet his power is STILL increasing?

He managed to land a clean blow to your face sending you flying back, you flipped a few times before landing on your feet.

Y/N: So you're more than what meets the eye...

Issei swooped down and began to walk towards you.

Issei: You're outmatched! Not even in my league!

Those last words pissed you off, you looked at him in the eye before speaking up.

Y/N: Out of your league huh...? HOW ABOUT THIS!!

You began to scream at the top of your lungs while gaining a golden aura making a massive gust of wind as the ground began to shake.

You soon went full on super saiyan before charging at Issei without warning, you began to swing at him as he didn't have enough time to dodge and tried his best to block, keyword "Tried"

You landed a clean blow to his face sending him flying back and through a nearby mountain, he soon flew out and charged you again while reeling his arm back. You did the same before the two of you rapidly smashed your fists together making a massive shockwave.

You put a little more power into your last swing making the arm piece of his armor shatter into pieces.

He held is arm in pain before you blasted him away with a Ki blast, you flew towards him before sensing a massive boost in power coming from Issei. He stopped before he gained a great red aura and his eyes glowed bright green. You crossed your arms in front of your face before being nearly blown away.

You watched as his Armor and body began to completely morph, soon enough he got bigger in size and even grew wings.

Y/N: Jeez...you're going all out with this huh? Well...

At this point, Rias and the rest of her Peerage showed up and watched in surprise at Issei's transformation.

Y/N: ...BRING IT ON!!!

Issei charged at you and reeled his claw back, you went to attack as well but he quickly scratched you, deeply cutting into your body, he then punched you away sending you through a mountain as well.

Issei let out a loud scream that caused him to make a huge storm of energy, he then flew towards you at insane speeds before wrapping his tail around you and slamming you into the ground before a crater formed and grew three times.

He let you go and looked down upon you, your now all beaten up body bloody face.

Y/N: G-Geez...You really are strong...

Issei: Looks like you'll have to join us...

Y/N: ...

Rias: Good work Issei! Finish him now!

Issei got his large claw ready before swinging it at you. It was an inch away from your face before you raised your hand and caught his claw faster than the eye can see. Issei tried to free his hand from your grip but it wasn't working.

Ddraig: Be careful...he's up to something!

He looked at you to see something about you was different. You looked up at him and have him a blank yet serious stare, soon you began to glow as your eyes did the same.

You let out a short but loud scream before Issei was hit by some sort of shockwave that sent him flying into a boulder.

Koneko: This is new...Rias, did this happen when you fought him?

Rias: No...this is something else...something very strong...

You stood up straight and stared at where Issei crashed, you then stared him down with your now angry looking eyes.

Y/N: I've won this fight...