That Swordsman (OP male reader x Highschool Dxd)

Chapter 1- I'm Back

*3rd person POV*
In the forest behind kuoh academy, a portal opens and out comes a certain person.

Y/n:Man, travelling through dimensions is harder than expected

Y/n:So the fuck am i

*Checks Phone*

Y/n:Phone says kuoh so I guess I'm in kuoh

Ascalon : I sense the old aura mark of Ddraig

Avalon : Yes. I sense it too.

Black : Should we search?

Y/n : Nah let's just find a place to nap. I be tired.

Black : OK. Let's go with this plan. We sleep then we search tomorrow.

All: Argeed

Y/n : look at that. It's a building. *Jumps in through window*DAMN! It looks old but sure as hell has some nice couches.

Y/n : Let's sleep!!!

"Timeskip to next day after school in kuoh academy"

Rias: *Opens door and sees Y/n sleeping on the couch*Who is this and how did he get in?

Kiba : Not sure. let's wake him up

*Riser Appears along with Grayfia*

Riser:Riser has come to claim his bride*looks at Y/n*who is this pathetic human? Shall I get rid of him for you?

Rias/Grayfia : No. Let's see who he is first.

Rias reaches for the blanket covering your face but you jump up, land behind her, put her in a armlock with Quickfang to her throat.

Kiba: *pulls out sword*Let go of the president now.

Koneko then rushes Y/n but he kicks her into a wall knocking her out. Rias tries to sweep your leg only to find it ineffective. Issei tries to attack but Ddriag warns him to stay put but Attacks anyways Y/n then proceeds to kick him into a wall knocking him out.

Y/n : Bring me Sirzechs. Now.

Grayfia: No. Why do you want to see Sirzechs.

Y/n: Well... If I don't see him, Devil Blood will spill. So. Where. Is. He.

Grayfia: Calm yourself. I'll get him now

Grayfia calls Sirzechs and explains the situation. A magic circle then appears on the ground and Sirzechs Appears. When Sirzechs looks at Y/n, Y/n surrenders Rias and they start walking towards each other. They then Raise their right fists and then they punch each other hard enough they fall to the ground.

Sirzechs:Bitch! You didn't tell me you were back!

Y/n:Well allow me to inform you then. I'm Back, BABY!

Sirzechs:After this, want to get some beers?

Y/n:Of Course!

Rias:Brother, who is this?

Sirzech/Y/n: You don't remember?!

Rias:I'm afraid not.

Sirzechs : he's the One you like from childhood till now?

Rias:Y/n! *Blushes Furiously*And I
don't like him!!!!

Y/n:Of Course! She only thinks of us as friends!

Rias: *Still blushing* Y-Yea!

Riser:Now Riser shall remove of this human so we can get on with this.

Sirzechs: Sorry but since he's back the original plan continues. Rias is to marry him.

Riser: Rias is to marry a weak human!
This is an insult to Riser saying that Riser is not on par with a pathetic human!

Riser then sets his fist ablaze and tries to punch Y/n but Y/n hardly flinches. Riser then increases the fire setting Y/n on fire but he just waves the fires away, surprising everyone. He then proceeds to punch Riser which sends him flying into a wall, Knocking him out. Sirzechs then proceeds to tell Riser's Peerage what to tell Riser when he awakes.

Sirzechs : OK. Rias and Riser can have a rating game but there is a 10 day training space. *Turns to Y/n* Can you train my sister please?

Y/n:Why not? I have nothing to do anyways.

Y/n then leaves with Sirzechs to get beers, Leaving Ddriag to explain why he told Issei to Stand down.

*Ddriag POV*

I didn't expect the wielder of one of the true longusis to be such a weak person producing little to no aura but underestimating him might be a grave mistake.

Rias: Ddriag. I have a question. why did you tell Issei to stand down?

Ddriag : I believe you don't know of the 13 true longusis?

All: what is the 13 true longusis?

Ddriag : The 13 True Longusis are Beings that not  Great Red or even God and Satan could defeat. They are extremely powerful capable of    wiping out entire planets with a snap of their fingers. But now it seems like they found their wielder.