Keep It Tight

This answer is the simplest. It requires you to do nothing but keep passively riding along and enjoying the pleasure that comes from it.

That pleasure only grows as Selena/Not-Selena wraps her legs around your waist to pull you in as deep as you can go and you tense your kegel muscles to hold on for just a bit longer. "Oh," you groan, "How I wish I could make you run away with me instead. Not to your kingdom but to some private place nobody could ever find us where you would be mine and mine alone. No longer a queen but simply my mate and mother of my children forever."

"I would!" Not-Selena/Selena gasps, their voices almost perfectly one now as they waver back and forth in time with how their flesh wetly slaps against yours, "I will! Do it, Darling! I would break happily! So, Darling... b-b-BREAK MEEEEE!"

Your penis twitches wildly at her words and you can no longer hold on, your teeth clenching as you thrust in one last time...

... and then everything but you, Selena, and the desk fade away to black as you begin firing off your load. As you cum, you can feel your Soul Rein tighten more than you have ever felt it tighten before, like a string pulled so taut it was only a second away from snapping. The Rein's pull sparks a massive orgasm in Selena as well, the pony-tailed blonde bouncing and quivering against you as the fertility runes that the dream replaced the cursed ones on her lower body with glow with a warm, golden light. You can feel the sensation of her cunt greedily milking you dry, even though you are sure that you are probably going to have quite the mess to clean up in your drawers in the morning.

Once the heat of the moment dies down, you look down at Selena and stroke her cheek. There. That should be some good payback for her lies and maybe you can get some more truths out of her about Artie, Parisa, and herself in the future. And it IS kind of thrilling to see her laying there, glassy-eyed and tongue sticking out of her mouth as she pants for breath. Her underwear is probably going to be quite the mess in the morning as well.

She eventually gains back some focus and looks up at you. Her eyes... have changed. Disturbingly, her irises have changed into a throbbing heart shape and a very manic looking expression starts forming on her face as she moans, "Daaaarliiiiing," she coos, "I loooooove yooooooou."

... Uh oh. Maybe things went a little farther than you had expected.

That is when your alarm clock sounds and the dream abruptly ends as you snap awake at the blaring noise. You groan as you sit up, feeling the stickiness around your crotch as you do so.

You do your morning routine, having to take a little longer in the toilet to clean up your crotch area. Once you are ready and changed for the day, you head out for breakfast. Before you can reach the cafeteria however, you are stopped by a concerning group made up of Headmaster Hallgrave, Professors Aspecta and Dove, and a woman in some kind of glittering armor that you recognize as Mana after a few seconds.

Before anyone can say anything, Mana suddenly storms forward as she glares **** at you. With no chance for you to react, she slams her metal clad, magically enhanced fist in your face and you are knocked out cold.

When you come to you find yourself on a cot in a jail cell... somewhere. Strangely, you do not feel the kind of pain you were expecting to feel from having been smashed in the face and when you catch a quick glance of yourself in the mirror over the cell's sink, you see that you have a mostly faded bruise over your nose but no real damage. How long were you out for?

"Good morning," you unexpectedly hear the voice of Aspecta say, "Before you ask, you were placed under a sleeping spell to keep you **** during transit after the Princess' bodyguard knocked you out and officially placed you under arrest. You have been out three days and are currently in a Tsukijin jail awaiting sentencing for your **** on a member of the royal family. I am here to verify you understand your situation once you awaken and officially discharge you from Ash Forest Academy."

"****?" you slur groggily, "I didn't do anything. She was in my dream and I couldn't--"

"The school investigated the situation," Aspecta snaps, cutting you off and you see she is looking at you with an expression that is a mixture of disappointment, pity, and something else a lot sadder, "It is true you do not have experience using dream magic so Princess Selena Lune should not have entered your mind even with your permission. Yet..."

She pauses, adjusting her glasses so the light hides her eyes from you, that sad, disappointed tone in her voice growing in strength. "Even if you had failed and the situation had ended the same way, had you even TRIED to struggle, made SOME attempt to try and stop things, we could have found the energies from that attempt and used that to defend you. But you didn't. You didn't even WANT to try, did you? You wanted something like this to happen to her."

You have no answer. She is not wrong and you cannot deny that. But what did she mean by "something like this"?

Aspecta looks over to the side and you follow her gaze to see another cell next to you. Inside of it is Selena, who is all but leaning against the bars, starting at you with a glassy-eyed but somehow needy gaze. "Darling," she mutters, "Darling. I love you, Darling. Mama says we can stay like this together, Darling. Maybe she'll even let us have a baby someday! I wanna have your babies. I wanna have 'em all. Babies... babies from my Darling..."

Aspecta sighs as she turns away from you. "She goes into a frenzy when she can't see you, refusing to do anything but get you in her sight. So for now, you get to stay together like this. That will only be until they undo what you have done to her. If they can. Mental damage this severe is difficult even for a kingdom known for its healing magics to treat."

A soft, grim chuckle comes from her lips as she adds, "If they cannot, well, she will hardly lay with the Prince anymore. Maybe they WILL let you have a chance to make at least one child with her to ensure the continuation of the royal bloodline. That is the most hope I can offer you though. Either way, I'm afraid that for you, this is..."