Soon after the Training is complete the Fallen Angels begin to attack Kuoh academy in droves ready to try and grab Issei's sacred Gear due to how Powerful it is, and of course, Their Leader Kokabiel led them.

Kokabiel: Yes! Yes! Search for him everywhere! That Sacred Gear will be Mine! I shall lay waste to devil Kind!

Fallen Angel: Uh, Sir?

Kokabiel: Yes?

Fallen Angel: All of our Soldiers are being beaten super quickly and even the weakest of them are taking out tens of dozens of them, also that Issei Guy with the Sacred Gear? Not even our strongest can beat him.

Kokbaiel: ......................................................

Fallen Angel: Uh Sir?

Kokabiel:

https://youtu.be/Re1WTdtRWZ8

Fallen Angel: What should we do sir?

Kokabiel then revealed A Holy weapon as he smiled.

Kokabiel: Well it's time to start Killing again, I suppose. Now Point me to the nearest-

???: No Way!

Kokabiel: Wha- GAAAAAAH!

Suddenly you Punched him so hard in the face he went flying into A Wall destroying it!

Kokabiel: Who the hell are you?

Y/n: I'm Y/n L/n and this is the Hell Bat Suit!

Kokabiel: Hell Bat suit Huh? What are you doing now? Barbatos?

Y/n: No I'm Much worse, Bub. 

Kokabiel: Cute Now get out of my way before I'm forced to- GAAAAAAH!!

You Punched him in the gut with A Power-stone-infused Punch!

Kokabiel: AAAGH! MY DIAPHRAM!

Y/n: GET THE HELL OUT OF THIS SCHOOL!

Kokabiel: Fine then Just let me pack up my stuff, and I'll Get going and- KILL YOU, YOU PIECE OF SHIT!

He then tried to Impale you with his Holy spear but it didn't even scratch your armor.

Kokabiel: Oh... Can I Please go?

Y/n: You Lost that Privlege.

You then charged A Large red energy beam in your chest and Fired it in A Huge Bat-shaped Blast!

Kokabiel: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAGH!!! Ugh... WHY ISN'T ANYONE HELPING ME!? Oh Right, they're dead... WHY ARE THEY DEAD!?

You then Grabbed Kokabiel by the Arm and smiled.

Kokabiel: Do I have any sympathy From you Left?

Y/n: You never had any to begin with.

Kokabiel: Oh... Shit...

You then did this to Him...

https://youtu.be/D9NywouA1I0

A/n: 3:18-3:27

Y/n: Whew! That Felt Good! Real Good.

You then got A Communication From Tohka.

Tohka: Hubby we got rid of all of the Fallen Angels.

Y/n: Good. I had Gotten Rid of their Dipshit Leader. We can take A Break after this.

Just then Rias' Own brother showed up to try and save everyone but he was A Little too Late.

Sirzeches: Alright Fallen Angels Prepare to- (Notices Kokabiel's Headless and Armless Body and then Notices you) Oh... You already did that right?

Y/n: Yes, I did.

You took your helmet off.

Sirzechs: How did you-?

Y/n: I simply saw this Event coming. Hi I'm Y/n Nice to meet you, Sirzechs.

Sirzechs: Uh, Right. You too. (Thoughts) This man is... Quite strong. Maybe he would be the perfect Husband for Rias.