"Hey, Rainbow! Are you in here?" you called, slowly opening her front door. If she was asleep, you didn't want to wake her, but at this point you had probably already done that with your shouting.

Slowly walking into the cloud house, the usual warm presence of Rainbow Dash was missing, instead replaced by a cold feeling on loneliness.

She wasn't in here. You searched every single room, including her room. Whether that was an invasion of privacy or not, you weren't too sure, but the fact of the matter was that Rainbow was missing.

You were about to leave and get some help, before Tank slowly but surely walked over to the front door, blocking you. Well, he wasn't exactly blocking you, but his presence alone was enough to stop you.

"Oh, Tank, you're still here!" you said, surprised by the tortoises sudden yet cautious appeareance, "Have you seen Rainbow Dash?"

The tortoise didn't respond, and you felt yourself becoming a little impatient. You weren't sure what you were expecting, as tortoises couldn't talk, even in Equestria.

Tank slowly turned his small head towards one of the houses many open windows, lifting one of his legs as if attempting to point.

Surely enough, outside the window you sure the blurred shape of a Pegasus pony slicing across the air, leaving her trademark rainbow contrail in her wake.
As it turns out, you were too focused on searching for Rainbow inside of the house, that you hadn't even bothered to check the outside.

"Heh... Thanks..." you thanked the tortoise, apologeticly rubbing the back of your head, before taking flight out the front door.

You weren't sure what she was doing out here flying around all by herself, but it most likely had good reason. Either that, or she was incredibly bored, as usual.

"Hey, Rainbow! What're you doing?" you asked, hovering stationary a safe distance away from her flight path.

No response. She must've been pretty engrossed in whatever she was doing.

"Rainbow!" you called, in a futile attempt to get her attention.

Once again, there was no response. Rainbow continued soaring through the sky, creating a knot of colours besides her cloud house.

"Rainbow!" you called, in one last attempt to get her attention.
Finally, you got her to stop whatever it was she was doing and turn to you, "What're you doing?"

Rainbow stopped dead in her tracks, taking in heavy breaths of air. It wasn't surprising, flying around that fast for that long would surely tire anypony out.

"Practicing..." she muttered between breaths. It had tired her out so much that she could barely even talk.

"For what, exactly?" you asked, curiously. As far as you knew, she had something planned for you, not something planned for herself.

"For... Today... Duh!" she panted, slowly floating down to your level. Whatever it was she had planned, you weren't sure it was a good idea to go through with it when she was this tuckered out.

"Andddd... What's happening today?" you asked, cautiously. Of course you were excited to find out what she was practicing for, but you were also concerned. If Rainbow Dash felt the need to practice, it must be a pretty difficult task to accomplish.

Suddenly, Rainbow grabbed you with her front hooves, beginning to shake you violently.

"We're gonna pull off the first ever Double Rainboom!" Rainbow screamed, seeming to regain all of her stamina in an instant.

"We're..." you could barely even comprehend what she had just suggested, "What?"

Rainbow continued to stare at you with the most hyped-up expression you had ever seen, rivalling even Pinkie Pie. She clearly had a lot of adrenaline built up for today.

"You heard me!" she replied, clearly wanting to waste no time with this.

"Yeah, but... I've only ever done one rainboom. How am I supposed to do a double one?" you asked, almost certain that you would fail.
At this point, you were practically dead set on the fact that you weren't even going to attempt it.

"It's just the same as when you did a Sonic Surge!" Rainbow suggested, attempting to persuade you, "Besides, I'm doing half the work anyway, right?"

She did make a good point. You only had to do one rainboom each, then that would equal a double rainboom. But still, you couldn't help but feel like such a thing as a double rainboom was simply a myth.

"I... Just don't think it's possible." you muttered, sitting down on the fluffy ground of Rainbow's front yard. She didn't sit with you, and instead remained hovering above you like a training coach.

"Aww, come on, Storm! Where's your confidence?" she asked, trying to maintain positivity even though you were making it quite difficult too.

As much as you really didn't believe it could be done, this clearly meant a lot to Rainbow. And hell, you didn't think you would be able to perform a Sonic Rainboom, but in the end you did it.

"Ok..." you said with a sigh, "We can try it."

As soon as those words left your mouth, you saw Rainbow's smile widen drastically.

"Yes! You're the best, Storm!" Rainbow exclaimed, swooping down and pulling you into a hug. She pulled away after about a second, not even reacting to it before she began talking about the double rainboom again, "Ok, so what we're gonna need to do first is find a good spot for it."

Almost instinctively, Rainbow began looking across the horizon, looking for a good place to attempt the rainboom. The best place for something as drastic as this was a place packed with clouds, as they could be used a crash pad in the event of a failure.

"Um... Rainbow?" you said, getting her attention instantly, "How about right here?"

You pointed a hoof towards the centre of her front 'yard', which was practically a giant cushion as it is. If you were to fail, you would have a few square kilometres to safely crash into.

"Heh... Yeah, that could work!" Rainbow laughed, looking down at the huge cloud that was her house, "Are you sure you're up for this?"

Did she really just ask you that? After just trying her hardest to persuade you to try it, she was asking you if you were sure about it?

"Hey, you're not changing my mind now!" you stated, adamant on the fact that you were going to attempt it. If you failed, so be it, but at least you tried it.
And even if you did fail, it wasn't like it was going to kill you. You had survived so many falls at this point that they practically didn't even harm you anymore.

"That's more like it!" Rainbow exclaimed, a beaming smile on her face, "We should probably have a practice run first."

Truthfully, you were expecting her to just dive straight into it. Literally. She had just been training outside for who knows how long.
But it made you happy that she was thinking of you, letting you get some practice in before the main event. You wondered what she could have planned. A short flight? An obstacle course?

"A Sonic Rainboom! Or... A Sonic Surge!" she suggested.

Ok. That was slightly more... extreme than you were expecting. But who knows, maybe you could make it work.

"Wouldn't that just tire us out?" you asked, attempting to find a reason to get out of this situation. You weren't against attempting a double rainboom, at least not anymore, but the thought of pulling off two Sonic Surges back-to-back just eluded you.

"Sure, it might. But it'll also give us the adrenaline we need!" Rainbow exclaimed. Surprisingly, she knew quite a lot about excitement and adrenaline, almost like she had studied it.
Of course, she almost certainly hadn't studied it. It wasn't Rainbow a Dash after all. More likely than not, she just knew so much about adrenaline from feeling it so often.

Once again defeated by Rainbow's reasoning, you agreed to doing a warm up Sonic Surge.

"Ok, fine. I'll try it." you said, with a sigh. Beginning to flap your wings, you sat up from the cloud and floated up into the air. Too your surprise, Rainbow didn't follow, and instead landed on the cloud you were previously sat on, "Aren't you gonna do it?"

"Nah. I've just done some warming up!" she explained, giving you a teasing smirk.

"What was all that about adrenaline?" you asked, beginning to get the feeling that she was just being lazy. Quite honestly, it wouldn't surprise you.

"Eh. I've got enough." she replied, stretching out one of her front legs.

Not even bothering to respond, you gave her a simple sigh, to which she responded to with a mischievous giggle. You knew she was only doing this to irritate you, but you also knew this was her way of teasing you.

She most likely did intend to attempt a double rainboom at some point today, but felt the urge to try and mess with you beforehand. Quite honestly, it was kinda funny seeing her attempts at getting under your skin.

Flying as high up as you could, the weight of gravity was already pushing you down. Relieving all of your effort, you let the natural forces of the world turn you around and begin pulling you down towards the ground.

The vapour cone was already forming around you, but this time it felt natural. It still felt like an added weight, but it seemed to be a lot easier to push through than last time.

Using a lot less effort than the previous Sonic Surge you had performed, the vapour cone shattered, releasing a burst of electrical yellow sparks across the skyline.
It was just as beautiful as last time, and quite clearly Rainbow though so too, as evident by her dropped jaw.

"How... Was... That?" you asked, between pants. By this point you were in a state similar to Rainbow when she had finished practicing.

"That was so awesome." she said, her gaze still locked on the spreading yellow shockwave in the sky, "Oh, yeah! Double Rainboom time!"

Before you could even process what was happening, she shot off into the sky with intrepidation, seemingly expecting you to follow her.
She turned around, giving you a confused look.

"Hey, are you coming or not?" she asked, becoming a little impatient. She clearly wanted to get on with this.

"Just... A minute..." you panted, causing her look of impatience to turn into that of compassion. She didn't seem too bothered now that she knew your reasoning behind not following her. She knew firsthand how much a rainboom could tire somepony out.

"Are you ok, Storm?" she asked, flying down to your side.

"Huh? Oh, yeah, I'm fine." you said, still breathing quite heavily, "Let's do this thing!"

You gave her a confident smile, too which she responded with her own concerned yet hopeful smirk. Despite not wanting to show it, you knew that your previous Sonic Surge had tired you out for the time being.
Nevertheless, you were gonna give it your all.

"Let's give it all we've got, ok?" Rainbow instructed, motivationaly, before flying up to you and matching you speed. You gave her a confident yet tired nod in response, attempting to regain as much staminate as you could during the build up.

The two of you stopped directly above her cloud house, planning to use her roof as a safety net in the event that one you falls. You both extended your wings outwards, preparing for what was about to happen.

"3..." Rainbow said, beginning the countdown.
"2..."
"1..."

There was no changing your mind now. Either you fly up there with her, or stay behind only to let both yourself and her down in the process.

"Go!" Rainbow exclaimed, before shooting off into the blue Equestrian sky. Instantly, you shot up after her, somehow matching her speed.
You were both too focused on the open air ahead of you to even acknowledge your synchronised flight.

Just like before, the forces of gravity had begun making their appearance. Out of the corner of your eye, you could see Rainbow rotating around in mid-air, preparing to build up enough force to shatter the sound barrier.
You copied exactly what you had done last time: flipping over to face the ground and flying with the force of gravity.

The two of you soared down towards the ground at mach speed, the wind tossing your yellow mane around like a rag doll. Maybe it was the fact that their was another pony next to you, but the wind had never been this intense the previous two times you had done this.

Before long, that same familiar vapour cone begun forming around your's and Rainbow Dash's hoofs. But instantly you knew you couldn't take it.

The two cones began to fuse into one as they grew, pulling both you and Rainbow towards each other. The unbelievable weight that this was putting onto you was borderline unbearable in your tired out state.

Almost like it was a gut instinct, you stopped. You stopped dead in your tracks, hovering in place as you panted for air.

"What the- Storm!" Rainbow called in annoyance, not seeming even remotely tired out. You weren't sure what training she was doing earlier, but it must have been some military training excersises if even this didn't tire her out.

Turning around, she saw the state that you were in and immediately regretted her outburst. She seriously cared about this double rainboom, but upon seeing you this worn out, she had this gut feeling to put you first.
Call it what you like: loyalty, pity. Either way, something deep down inside her was telling her to put you first.

And she listened to it.

"Hey, come on, don't go crashing down on me!" Rainbow said, in a somewhat gentle tone as you felt your wings begin to give out.
Were you... falling asleep?

"Woah!" was the last thing you heard her say. The last thing you felt was your wings completely stop flapping, and a pair of gentle hoofs catching you, holding you tightly in their embrace.

All you knew at this point, was that everypony has their limits.

Maybe you had found yours?

Author's Notes:

There isn't really much to say about this chapter. It's pretty much all on the can. Rainbow wants to attempt a double rainboom, Storm isn't sure it'll work. Sure enough, it ends somewhat badly (at least for Storm, anyway).
Just a little TLDR for ya.

I actually finished this chapter yesterday, but chose not to upload so I could get a little bit ahead. Always good to have things prepared in advance