Alright, so as you can probably tell by the title and the description, this is also a crossover with the Flash tv series. This was just an idea that popped into my head after I saw the Volume 3 finale.

This takes place during the events of RWBY V3E12 and after the events of the Flash S2E15. EDIT: Also takes place after the Flash's crossover with Supergirl.

Disclaimer: I do not own the Flash or RWBY.

Just outside Beacon, Nora, Ren and Sun watched over the prone forms of Blake and Yang. The former was barely clinging to consciousness while the latter was out cold. Everything had gone to hell so far: The Grimm had invaded Vale, Beacon was under assault by the White Fang and now, Ruby and Weiss had left in order to find Jaune and Pyrrha.

"That's it." Nora said. "I'm not waiting anymore, I'm going to help them!"

Ren nodded in agreement, and the two of them moved to get up, only for their injuries to act up, causing them both to groan in pain.

"You guys aren't going anywhere." Sun said sternly. "Ruby and Weiss can handle themselves." He said, much less confident in this case. "I hope." He muttered.

Blake lifted her head slightly, her gaze shifting to something past the landing pad. Her eyes widened in surprise.

"Does anyone else see that?" She pointed down towards the bottom of the cliff causing everyone nearby to turn in confusion.

What they saw shocked them all: from what they could see, it almost looked like some sort of portal or breach in the middle of the air. Much like the portal Weiss had recently used to summon that sword arm, but it looked like it was in a state of flux, ironically also looking more natural.

"What... is that?" Ren said in shock. For once, Nora had no words.

The breach was blue-white in colour, and was constantly shifting. It was like nothing anyone had ever encountered on Remnant. Eventually others started to notice the breach as well, the evacuation almost halting as people tried to take a look. Even Professors Port and Oobleck were drawn to what everyone was looking at.

"My word," Oobleck muttered. "What a shocking scientific anomaly!"

Before Port could respond, another flicker of movement caught everyone's attention as the portal disgorged someone. It seemed to be a human, clad in some sort of red bodysuit. The man looked around seemingly confused at his surroundings before looking straight up at the landing pad.

"Who is that?"

"Where did he come from?"

"Is he part of the White Fang?"

These were the mutterings of all the witnesses, which were abruptly cut short when the massive Grimm Dragon flew overhead. That got everyone moving again.

"Everyone move along." Port said. "No need for pushing, there's enough room for everyon-"

His order was interrupted when a streak of yellow lightning emerged from underneath the landing platform, moving past everyone at an impossible speed, causing a brief wind to form in its wake.

"Onto the ships." Oobleck ordered, more sternly this time. "No time to waste."

None of Team RWBY or JNPR were in a rush to follow that order however, as they noticed that the portal had vanished, the man had disappeared, and the lightning was heading in the same direction as Ruby and Weiss.

Weiss watched as Ruby scaled her glyphs up to the top of the tower. She could only hope her team leader could get up there in time before Pyrrha got herself killed. Considering how Jaune sounded on her Scroll, Weiss could only imagine how he was feeling right now.

Jaune was Pyrrha's leader, and yet she was fighting alone against Cinder, the murderer who was responsible for this whole mess. If Pyrrha died, the Schnee heiress was terrified that Jaune would never forgive himself, even though it wasn't his fault that Pyrrha went in alone.

As Ruby approached the top of the tower, Weiss heard the Grimm approaching behind her. She turned to regard the threat when something unbelievable happened. A streak of yellow lightning plowed through the approaching Grimm, sending dozens of them flying.

While the Schnee heiress was surprised at this, what was more surprising was that the lightning didn't stop, running past her at speeds even Ruby couldn't hope to match. Spinning around, Weiss was able to catch a glimpse of the seemingly sentient lightning just as it vanished over the precipice of Ozpin's destroyed office.

In the office itself, Cinder Fall had just finished a brutal beatdown against Pyrrha Nikos. The champion from Mistral had put up a valiant fight, Cinder couldn't deny that. Ozpin would've been proud if he had seen it.

Still, Pyrrha was no match for the powers of the Fall Maiden, and now she was on the floor, beaten and broken, having taken an arrow through her heel. Cinder circled the fallen champion, creating her obsidian bow as she walked in front of her.

"It's unfortunate you were promised a power that was never truly yours." Cinder knelt down and lifted Pyrrha's chin, staring into her eyes and smiling wickedly. "But take comfort in knowing that I will use it in ways you could never have imagined."

Pyrrha pulled away, sitting up and steadily matching Cinder's own gaze.

"Do you believe in destiny?" Was all she said.

Cinder frowned and her eyes narrowed. A single tear appeared before she blinked it away.

"Yes."

There was nothing more to say. Cinder cocked her bow and had an arrow pointed at Pyrrha's heart, while the young champion was on her knees and helpless. Dimly, the two warriors became aware of Ruby's arrival in the ruined office, but there was nothing she could do to stop this. With a wicked grin, Cinder let go of the bowstring.

No one on Remnant could've predicted what happened next.

All Cinder and Ruby saw was a streak of yellow lightning as Pyrrha... simply vanished. The new Fall Maiden's eyes widened as her target disappeared and her arrow flew off the edge of the building. For once, Cinder was at a loss to explain what happened.

Then everything went wrong when Ruby screamed.

"PYRRHA!"

Jaune ran through the deserted streets of Vale, ignoring all the sounds around him. His only goal was to get back to Beacon immediately. His heart was pounding as he ran, but he ignored as he focused on his one goal.

His mind was racing, his thoughts spinning like a hurricane. Yet there was one thing that stood in the eye of the storm, the one thing that granted clarity in his mind.

Pyrrha.

He had to get back to her. Jaune didn't want to lose her after all that happened today. Pyrrha had been his closest friend since he arrived at Beacon. She was the only who knew that he had faked his transcripts into Beacon. She was his partner, who he had trusted with his life time and time again.

He had done all he had could to help raise her spirits even though she wouldn't tell any of them what was bothering her (though now, Jaune had a pretty good idea as to what it was). He had stood by her Ozpin was putting her through that process and had tried to defend her when that Cinder woman showed up.

And when she had kissed him... Jaune didn't know how he had been so blind. To both her feelings and his own.

The raging storm in his head was halted when, suddenly, a bright silver-white light erupted from the direction of Beacon, momentarily blinding him and every human, Faunus and Grimm nearby.

"PYRRHA!" He shouted.

When the light disappeared, Jaune could see the massive Grimm Dragon perched on the side of the tower. Strangely, it seemed like the massive creature had been... frozen. But that observation meant little to him, as he knew there was no way that Pyrrha could've survived if she was still up there.

Falling to his knees, Jaune could do nothing but stare helplessly at the sight of Beacon's main tower. He felt a void growing in his chest as it slowly dawned on him that he lost the person he hadn't realized he had been in love with until today.

That void lasted for all of five seconds before a streak of yellow lightning blasted past him, with the resulting jet stream forcing him to shield his eyes. Then he heard someone groaning in pain, followed by a familiar voice saying his name.

"Jaune?"

"Pyrrha?"

His heart threatened to leap through his chest when he saw that she was alright, though it nearly broke when he got a look at the extent of her injuries. Leaning against a wall, with blood leaking from her heel and her Aura completely drained; She looked like she had just been through hell, and considering her opponent, she probably had.

"Oh god, Pyrrha." Jaune whispered, rushing towards the redhead as she struggled to stand.

He wrapped his arms around her and she reciprocated. "Are you alright?"

She shifted in his grip, gingerly supporting herself in his arms. She groaned as she tried to stand on her injured leg, drawing Jaune's concerned gaze to her face. When their eyes met, her expression softened.

"I'm fine now." Was the only thing she said.

They were silent for a moment before Jaune kissed her, and in an interesting reversal from earlier, she was the one who was surprised at the gesture, before her hands cupped his face and she deepened the kiss.

Relieved, she melted into his embrace. The two of them stayed that way for a long time and both felt like they could stay there forever. The moment was lost when they heard growling behind Jaune.

Opening her eyes, Pyrrha broke off the kiss and gasped when she saw four Beowolves and an Ursa approaching them. Spinning around, Jaune quickly pulled out his sword while also supporting Pyrrha with one arm, but it was clear he was outmatched, and she herself had sustained too many injuries to fight any further.

Before the Grimm could do anything, the yellow lightning returned, sending all five of the Grimm creatures flying. Once that was done, the lightning abruptly halted, revealing the source to be a single human.

He was clad in a red full body suit, with yellow accents around his waist, and strange lightning bolt-like antennas emerging from the mask that covered most of his face, leaving only his eyes, nose and mouth uncovered. A strange symbol sat on his chest: a yellow lightning bolt inside a white field within another yellow circular outline.

"Are you guys okay?" The Scarlet Speedster asked. He had a very young voice, yet still older than most of the students at Beacon.

They could only nod in muted shock. They had never seen anyone with this type of power before. Even Ruby couldn't move that fast with her own semblance, but something told Pyrrha that this was not an ability created by this man's soul.

"Ok, good." The speedster replied. "You need to get somewhere safe." He briefly turned his head before Pyrrha interrupted him.

"You were the one who saved me?" He nodded, with a look of confusion.

"Why?" She asked. "And how did you even know anyone was up there?"

The man in red opened his mouth to reply when he heard a small thunderclap behind him, and saw Jaune and Pyrrha looking past him. Turning his head, the speedster saw a blue-white portal opening several blocks away.

"Zoom." He whispered, before turning back to the two teens. "I have to go." He said sadly. "I'm sorry."

"Wait!"

"Hold on a second!"

But it was too late. Their shouts followed the costumed hero as he seemingly turned into lightning and vanished into the vortex. Less than a second later, the portal sealed, leaving no trace of his existence.

"Jaune! Pyrrha!"

The two teens turned around to see Nora, Ren and Sun heading towards them. The two other members of Team JNPR were limping, clearly from injuries they had sustained earlier. Still, looks of relief were etched onto their expressions as they met up with their team members.

"Thank god you're alright." Ren said, limping as he walked. "We were so worried about you guys!"

"We're alright." Jaune said. "We're both okay now."

"Oh my god, did you see the lightning?!" Nora all but screeched, immediately wincing and clutching her side before lowering her voice. "I"ve never seen anything move that fast."

"Yeah, we saw him." Pyrrha replied. "He was the one to get me off that tower." She gestured to the Dragon perched on Beacon.

"Wait, he?" Ren clarified, but was interrupted by Sun.

"Look, as interesting as this is, we need to get outta here." The Faunus interjected. "Pyrrha, can you walk?"

"I-I think so..." The Mistral champion took a step forward, only for the pain in her heel to grow worse.

Stumbling, she was caught by Jaune. "I've got you." He said, picking her up and carrying her bridal style. Pyrrha couldn't help but smile in spite of herself, something Jaune easily returned.

"Let's go." He said, walking with her in his arms, followed closely by Sun.

Nora and Ren watched as Jaune carried Pyrrha to the evac point, sly grins on both of their faces. At least something good had come out of this horrible day. Then they followed their teammates out of the city.

As Team JNPR and Sun made their way out of the city, none of them bothered to look behind them as they left an army of Grimm milling about. As a result, no one saw the streak of red lightning as it slammed through a dozen Grimm, killing them in seconds.

None of them saw as the lightning also halted, revealing the source to be a man with a similar costume to the Scarlet Speedster. The main difference included a reversed color scheme of mostly yellow accented with red. The man's whole body was vibrating at an unnatural pace, and his eyes were also glowing red.

The man in yellow watched as the Atlesian ships took off into the air, an unreadable expression on his face. Abruptly, a small thunderclap erupted from nearby and he turned to watch as another portal appeared in the middle of the street. He smirked at the sight.

"See you soon, Flash."

An unnaturally deep, distorted and outright monstrous voice emerged from the masked figure. And just like his counterpart, the speedster disappeared in a streak of red lightning, and entered the portal, which promptly vanished.

I don't know why I put Reverse-Flash in there at the end, it was just something that came to me. Anyway, I know the Flash's arrival and departure in this was kinda abrupt to the point that it was essentially a Deus ex Machina, but that sorta thing would happen if someone from a completely different universe appeared out of nowhere.

Now, to answer a couple details:

Why does Ruby react the same way when she arrives on the tower itself?: Look at it from her perspective; all she saw was Cinder firing an arrow, a streak of lightning and Pyrrha vanishing. She still doesn't know what Cinder's powers are capable of, and without context for the Flash's existence, all she can assume is that Cinder disintegrated her. With the emotional pain of that thought, the fact that Cinder is confused about Pyrrha's disappearance wouldn't really register.

Why doesn't Ruby save Pyrrha herself?: I've heard that asked before, and I've considered that idea. The problem; Ruby hasn't had a chance to rest since her encounter with Mercury and is almost certainly tired from everything afterward. Plus, she reaches the top of the tower at the exact moment that Cinder fires her arrow, so by the time it would register to Ruby, it would be too late to stop it. The Flash on the other hand, is not only faster than Ruby, he also has accelerated perception, so he would see the arrow moving in slow motion and be able to react quickly enough to do something.

EDIT: I should clarify that this Flash is Barry Allen, not Wally West.

Anyway, I hope everyone enjoyed this one-shot and reviews are always welcome.