You were using your cubes to open a gateway to Issei's room.

Issei: "Y/N. I... I felt something during the entire rating game. That was you, right?"

"Not intentionally, but I did see the whole thing. I'm going over to Riser's place and get Rias back."

Issei: "Count me in. Asia, we'll be back in a while."

Asia: "Take care you two."

"Asia, do you have any Holy Water?"

Asia: "Uh, yes."

She left the room for a bit and brought back a vial of Holy Water. You grabbed it and put it in your jacket.

Issei: "You've been training as well, haven't you?"

"I had to test the limits of my new powers. Turns out creativity is very beneficial with an ability such as this."

Issei: "Sounds awesome. Let's do this."

You nodded and activated the teleportation circle, sending yourself and Issei to the engagement party. You came across a bunch of guards and fought your way through them before you fired an energy shot to blast the doors open.

Rias, her peerage, and the attendees looked on in shock to see you and Issei breaking in.

Rias: "Issei! Y/N!"

"We're getting you out of here, Rias!"

Riser approached you.

Riser: "How dare you two break in--"

"Riser Phoenix, correct? Hand over Rias right now. She doesn't belong to a scumbag like you!"

More guards surrounded you to attempt to subdue you, but you used your cubes to knock them away.

Sirzechs: "The entertainment arrived sooner than I expected."

Rias: "Big Brother!"

Issei: "So that's Sirzechs?"

Riser: "Sirzechs, what do you mean by entertain--"

Sirzechs: "The rating game was very interesting to watch. However, against my sister who was inexperienced and had half the pieces, I decided to have something extra for this. I personally invited a certain Y/N Redgrave to come and take my sister for himself if he truly wishes to prove his strength in spite of not being affiliated with any household."

"Gladly."

Rias: "Y/N, don't do this."

Riser: "Very well. You'll be my last flame before I settle down as a married man."

Sirzechs: "Alright, Redgrave. What do you want as a reward for winning? What is it you desire?"

You thought for a second and remembered the smile Rias gave you.

"I want Rias Gremory."

Sirzechs: "Then take your positions."

You and Riser teleported to a small arena above the mansion.

Riser: "I know you're no devil. You're just a lowly human. I'm going to enjoy killing you."

"Better hope I don't take my time with you."

Sirzechs: "Begin."

You summoned his Crown of Dominion and charged at Riser as he formed his wings and flew away. You fired multiple energy missiles at him, but he managed to dodge them.

With the Astral Wings on your back and a gauntlet formed around your hand, you punched Riser so hard, he got knocked back a bit, but he retaliated by smashing you to the ground.

Riser: "You think you can defeat me with a bunch of pathetic powers? This is our clan's gallant hellfire of the phoenix, the firebird, the immortal bird! Burn before the flames!"

You charged at him and dodged the attack before forming a sword on the back of your hand and slashing Riser's back. He kicked you into a statue, but you got up just as quickly and spit up a little blood.

You closed your eyes and communicated with Pandora.

Pandora: "You wish to use the next step of your power? You are not strong enough yet. I can make it so the repercussions won't be too severe, but you won't be able to use it for long."

"That's fine by me."

Pandora: "I can see why your father and best friend are glad for you. Now show the Phoenix the true might of the Astral Dragon!"

You returned to reality and a burst of energy came from yourself.

Riser: "What is this?!"

You struggled with the pain as Astral Matter materializes and fused with you. Cable-like objects then appear and "connected" to yourself. As the Astral energy flew through your body like circuitry in machines, armor transformed around yourself in the style of armor fit for a ruler.

"Let's end this, Riser," you said in a booming voice.

You zoomed in front of Riser and punched him through the walls of the arena.

Riser: "I... actually felt that! Now you must die!"

He formed a massive ball of fire and threw it at you, but you charged right through it and sped towards Riser while throwing punches at each other. You were hurt rather badly, but Riser acted all smug until he coughed up blood.

You both started falling, and Riser sensed a holy aura in your arm.

"Oh, I might have been holding a cross when my armor was forming."

Riser: "Damn you!"

Riser attacked as you made a cut on your arm, then grabbed the holy water Asia gave you earlier and threw it into an Astral cube you formed. The cube turned into multiple daggers and impaled Riser before exploding, causing him to scream in agony. From your distance, you saw Riser trying to recover, but the pain caused by the holy items has diminished his energy and spirit.

"Well then, let's end this."

Riser: "W-Wait! This engagement is important for the future of all devils! A kid and human like you who doesn't know anything has no right to interfere!"

"Wow, I really pushed you into a corner, didn't I?" you said sarcastically. "I don't give a damn about the future of the devil race or this three factions shit! When I saw Rias through Issei's eyes during that damn game. I saw her crying."

After a flashback of Rias crying and smiling during the game, you charged at Riser at full speed.

"That's more than enough reason for me to end you, Fuckface!"

You delivered the coup-de-grace by punching Riser in the stomach.

Riser: "You bastard! This can't be happening..."

You walked up to Riser and threw the cross into a cube that turned into spinning blades. During this, a short, blonde-haired girl ran into the arena and tried to protect Riser.

"Don't hurt him!" she shouted.

Issei jumped into the arena and pointed his boosted gear at the girl.

Issei: "I'd suggest you back away and let them settle this, little girl! If you have any complaints, come at me! I'll gladly take you on!"

The girl blushed a little and you saw an image of when Issei was the only one in this moment.

"Has all of this happened before?" you thought.

Suddenly, the gravity shifted and everyone fell from the arena. Koneko caught Issei and Rias caught you.

"Rias?"

Rias hugged you tightly.

Rias: "Y/N! Thank you, Y/N. You saved me!"

"My mom told me always protect what was worth fighting for."

Everyone landed on the ground and a dragon-like creature made of Astral Matter appeared in front of them.

Issei: "Woah! Where did that come from?"

"A friend sent it. Rias, mind if I escort you back to Earth?"

Rias: "I'd love that."

She held out her hand and you grabbed it to help her onto the creature. You took off as everyone waved at you.

Issei: "We'll see you back at the club room."

Meanwhile, Sirzechs and Grayfia watched as you and Rias flew away.

Sirzechs: "My theory has been confirmed. The Astral Plane and its master exist. All of this has happened before, but not exactly like this."

Grayfia: "Then the future is very uncertain at this point."

Sirzechs: "Maybe, but it'll be worth seeing."

You looked at Rias and saw that something's on her mind.

"You don't have to worry Rias. You're safe."

Rias: "For now. The engagement has been canceled, but with the current state of the devils, but another engagement proposal can come at any time."

"Everyone will come to your defense when that happens. And that'll go triple for me. I'll come save you no matter how many times."

Rias blushed in surprise at your words.

"Besides, I want to know more about the devil world. I'm starting to see the beauty in it."

Rias leaned in close and kissed you.

"That wouldn't happen to be your first kiss, would it?"

Rias: "It is, but consider it a reward for saving me."

"I have a feeling I traumatized Riser."

Rias: "Just a little. But can I tell you something?"

"Sure thing, m'lady."

Rias: "I've decided to live at your house."

"My house?! Are you for real?"

Rias: "I don't want to interfere with how things have been between Issei and Asia. Also, I think it's high time I get to know you more."

"Alright," you said after your mind comprehended everything she said. "Let's talk to my dad first."

Rias: "Good idea."

As she hugged you, you thought to yourself "This girl is really something".