A/N: This chapter is a modified version of the Supergirl episode 'World's Finest' that shows the true sparking feelings of both Barry and Kara. The first few chapters will summarise the lead up events and be more the background of the story.

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National City

Kara was on her way to Catco with Ms Grant's coffee in hand reflecting on the recent events in her life and how she could possibly be able to win back the trust of National city. As she walked into Ms Grant's office she handed her, her coffee and went to walk out to her desk.

"Aren't they exquisite?" Ms Grant asked.

Kara turned back realising that she was talking about the box of cupcakes on the desk. "I can see it in your eyes that you want one" Ms Grant continued, "but you're too scared, so instead you stand at a distance gazing longingly from a safe distance wishing you had one all of your own."

Ms Grant continued to explain how she wouldn't be able to get a cupcake unless she did something about it. Kara, confused, continued to listen until she realised that Ms Grant was actually talking about Jimmy. Kara tries to avoid the conversation but seeing an opportunity to gain advise on how to resolve her situation she asks for her boss's opinion.

Ms Grant tells her that in order to get Jimmy that she should make herself seem unavailable by finding another man. Kara acknowledges her suggestion then reaches across for a cupcake only to be rejected by Ms Grant then proceeds to rush out of the office in thinly veiled embarrassment at the conversation.

Kara returns to her desk and get back to work. Soon after she looks up hearing a commotion only to see Siobhan Smythe walking toward her. Ms Grant calls from her office for Kara to call security and as she does Kara stands up to talk to Siobhan and get her to leave peacefully.

As Kara does this Siobhan turns to her and screams, throwing Kara back and out through the window behind her.

Central City

Barry is in the labs talking with Wells, Cisco and Caitlin preparing to test out the new device they made from the schematics they got from The Reverse Flash. Wells walks up to Barry and attaches the Tachyon Device to his chest over his symbol telling him that it should increase his speed and give him at least an even standing against Zoom.

Cisco tells him that everything is ready to go for the test run and Barry gets into a ready position. As Barry gets ready to go, he feels the familiar sensation as the Speedforce courses through his body but this time he feels a stronger connection to the power and when he moves, he can already tell he is going far faster than usual.

Cisco's voice sounds distant through the com as he yells about how fast he is going but Barry isn't listening as he races through the streets of Central. As he gets caught up in the feeling of running at this newfound speed and revels in the opportunity this gives him to defeat Zoom and fix what he believes was his own mistake, he doesn't notice the blue portal opening in the distance.

Distracted, Barry runs through the portal and finds himself in the middle of a city that seems off and is around late morning as opposed to the night he just left from in Central.

Without time to properly understand what's going on or slow down he sees a woman being thrown through a window of a nearby high-rise building that has the name Catco written across the top. He instantly races up the side of the building, catching the woman and before he can comprehend what's happening, he has already run out into the desert surrounding the city. Stopping, he puts down the woman only to realise her shirt is on fire.

"Oh my" Barry exclaims, "you're on fire!"

Despite the situation the woman doesn't seem shock and rather says that she needs to get back to the city before flying off back the way they came with her burnt clothes dropping down onto Barry.

Confused at what is happening and where he is Barry decides to follow the flying woman back towards the city in order to gain some idea of what's going on. As he runs, he sees the woman approaching the ground so redirects himself to stop where she lands.

As she lands, he gets his first proper look at her and notices she is in a costume with a cape, but he notices little else as he is caught up looking at her deep blue eyes and for an unknown reason he is captivated by the beautiful blonde before him.

She introduces herself as Supergirl, sounding as if he should clearly know who she is. Supergirl then asks what happened seeming confused on how he saved her and who he was.

Barry answered by explain how he run and caught her then brought her out to where they were by accident. Usually, at least when he is out as The Flash, Barry finds himself being confident but in the face of this new person he finds himself stuttering, and despite his confusion at the situation, he is nervous when talking to the beautiful woman before him.

"I'm sorry, who are you?" Supergirl interrupts his stuttering with a confused look on her face.

"I'm the Flash" Barry responds but upon seeing her confusion he goes on to list other heroes such as black canary, Green arrow and A.T.O.M.

"er, I'm sorry I don't know any of these people" she answers.

Barry realises that the portal he travelled through led him to another Earth. Taking off his cowl he says, "not as sorry as I am. Hi, I'm Barry Allen, the fastest man alive, and I think I'm on the wrong Earth and I'm going to need your help"

-----

As Kara falls from the Window and is caught by the strange man in red, she finds herself in a daze from the scream that had thrown her from the office. Confused she tries to figure out who the man is after landing and confronting him.

After saying a bunch of names that she doesn't understand the man reaches up and takes off his cowl explaining who he is and that he's lost and from another Earth.

Usually in a situation like this Kara would find herself even more confused and analyse the other person to see if they're a threat or not but in this case she doesn't. As the man, introduced as Barry takes off his cowl, she finds herself caught up in the man's handsome face and finds herself feeling an attraction that she hasn't felt before, even with Jimmy.

The handsome man asked for her help and despite knowing almost nothing about him she knows that she is going to help this man, so she asks him to meet her back at the office she left in her special room that's set up for Supergirl stuff.

-----

Barry goes back to the building that she had been knocked from and when he arrives, she introduces herself as Kara Danvers, having gotten changed from her suit into clothes she had left at the office.

Barry uses the computer to figure out what is different about this world and tries to find Wells or Cisco but to no avail. As he stresses about what he's going to do two men walk into the office, one is a tall, bald and muscular black man and the other is a short Man who seems relatively lanky.

The men continue to explain what happened after Kara was thrown from the window and then proceed to question who he is and what he was doing there. Barry introduces himself and finds out that the black man is named James Olsen and the other is named Winn.

As he introduces himself Winn questions where he is from and reveals that Kara is an Alien. Kara looks away embarrassed not want the new man she met to dislike her for being an alien. Hearing no response, she turns back to see a smile for on his face and he begins excitedly questioning whether there's other aliens on this Earth.

See how Barry acts when finding out she is alien only results in her unknown sense of attraction to grow as he accepts her being an alien without any doubt or second guessing.

Barry continues by explaining the multiverse and how he is from a different universe and although he is telling all three, his attention is focused on Kara looking to see her reaction and what she thinks.

As Barry explains Winn jumps in adding that if someone were fast enough, they could theoretically open a portal to another universe.

Kara watches Barry with rapt attention, fascinated by this new person and wanting to know all she could about him. As Winn questions how he managed to get to their universe Barry responds by running from the room and returning shortly after and Kara finds herself and the other two with ice creams in hand.

Barry smiles as he sees Kara's face light up as she giggles and begins to eat the ice cream. Barry then explains how he got speed and how he managed to accidentally breach to their universe but is now stuck due to not knowing how to purposely create a breach.

Kara smiles and walks up to Barry placing a comforting hand on his shoulder reassuring him that she will help him any way she can. Kara feels herself heating up at the close proximity to Barry and blushes removing her hand.

Barry smiles back to her and seems to cheer up at the reassurance but gains a concerned face before explaining that he needs to consume at least 10,000 calories a day with an embarrassed face looking around nervously, afraid that Kara, the girl he has found himself captivated by, may think he's weird.

"You've met the right girl then" Winn exclaims.

Kara blushes as she looks at Barry asking whether he likes donuts.

"who doesn't?" Barry responds.

Kara smiles then grabs his hand instinctively and drags him with her to go and get donuts.

-----

After being caught up whilst leaving in Ms Grants office on the way out and her deciding to name Barry's superhero alter ego, The Blur, Barry and Kara headed out and went into a nearby donut shop where Kara ordered two dozen donuts.

As Kara and Barry sat together at the donut shop, they discussed about their superhero experiences and what they have been doing recently. Both avoided talking about the big things like Zoom, the Red K experience and Non but found each other really easy to talk to.

Both heroes were enraptured by one another and despite neither knowing it themselves, it was obvious that the two had feelings for one another and they seemed as if they were at least close friends meeting up after a while apart.

After eating they both returned to Catco where Barry went to the Supergirl room to try and find a way back to his Earth, whilst Kara went back to her desk feeling excited about how amazing she found Barry and how close they were getting.

As she was at her desk organising her bosses schedule, she got a call from Lucy Lane, the temporary director of the DEO, that Livewire had escaped holding and was on the loose and likely coming for Cat Grant.

When Kara got off the phone, she rushed into Ms Grant's office and explained the situation suggesting for her to go someplace safe that she'd organise but instead her boss said she wouldn't hide and that if she needed it Supergirl would protect her.

-----

As Barry was on the computer doing research whilst James and Winn were standing around the room, with Winn firing him questions every few seconds about his life, Kara came bursting through the door with a worried look on her face.

"I need your help" Kara said.

James responded thinking she was asking for him, but Kara clarified saying she was asking Barry for help. Kara explained the situation she was in and he National City needed the flash. Hesitant at first to take too long when finding a way back to his Earth Barry quickly conceded knowing that he'd do whatever it takes to help Kara although not quite understanding why.

Kara lit up as Barry said that he would help her and was excited that she would have the opportunity to work with Barry and she felt a strange feeling in her stomach like butterflies were in there as Barry smiled and shook her hand saying "partners" to which she responded in kind, shaking his hand.

-----

After agreeing to help, Barry and Kara headed to the DEO facility with Winn were Barry ran around fascinated by everything there and even more thrilled when he found a space ship that Kara claimed was hers.

Kara was feeling even more weird emotions as she watched Barry run around thrilled by the place she worked and, although she didn't quite know why, Kara was happy that Barry liked the place she worked and was accepted by the people she worked with.

After introductions were over Barry explained how he protected people in both his day and night job as he was a CSI. Barry then got to work on using some of his skills to try and find Livewire whilst Kara and Winn watched as they talked about what his day job was like.

The algorithm soon found where Livewire likely was. As it sounded the notification Lucy and James, who had just come in and was talking to Lucy, came over and ask what was happening. Barry and Winn explained how they had found Livewire using the electricity levels in meters across the city.

Kara, seeing the opportunity to take down the threat as well as to impress the new speedster in town said that they should both get going to take her down.

"So, what's the plan?" Barry questioned.

"Take down the bad guy, lock her up where she can't hurt anyone. 85% chance of punching." Kara responded, looking to impress Barry and thinking given she took Livewire out once she could do it again.

After Barry questioning that they should have a proper plan of action but Kara saying it was too important that they act now and that they need to go, Barry follows Kara saying that it will be ok and that he trusts her.

-----

Kara raced towards the warehouse as fast as she could wanting to impress Barry with her speed and arrived there just before Barry.

"For the record, I was here first" Kara told Barry. "For the record I went around the perimeter first to technically I was here first" Barry responded.

Enjoying the banter but looking forward to the fight the superheroes gets back on task looking around the warehouse for Livewire just before she comes out of a bunch of lights to form in the middle of the building in front of the two.

Barry says he's got this and races around the villain, building up power to then throw lightning in order to overload her although it doesn't go to plan as he charges her up only for her to throw the lightning back at Barry throwing him back up onto a wooden platform behind him.

Kara, seeing Barry hurt and worried for her new friend turns to Livewire and spots a sprinkler above her head and goes to set it off with her heat vision only to be stopped by a piercing scream. The pain forces Supergirl to kneel as she puts her hands on her ears, removing them when the sound ends, she finds blood on her fingertips.

Looking up she sees Siobhan who names her self the Silver Banshee saying that she will kill Supergirl then go on to get revenge on Cat and Kara for her loosing her job. Seeing the two together she goes to use her freeze breath and in joined by the Flash who uses his arms to create to mini tornados to join her in blowing away the two villains.

Knowing that they probably won't be able to get out of there Barry shouts to Kara saying that they can't win this now and that they need to leave. Kara agreeing the two heroes leave with Kara flying out through the roof and Barry running out the side of the warehouse.

-----

Barry returned to Catco after passing through the DEO to grab his change of clothes. When he arrives, he sees Kara standing out at the balcony and walks out next to her.

"Hey, how're you doing?" Barry asks.

Kara looks up at Barry for a few seconds thinking what to say, "I'm sorry, I made you run in there without a plan, I didn't expect there to be two of them." Kara answers in a sombre tone.

"It's ok, it's what we've got to do, prepare for the unexpected."

"something happened to me a few weeks ago. I was exposed to this substance and it made me crazy, I did a lot of horrible things. When I was doing things as Supergirl I was so happy but now when I go out there no one wants my help. No that the people don't want to me to help them I feel so lost. I'm in such a rush to prove myself I'm making dumb mistakes like today"

"this will sound ironic coming from me but, sometimes you've just got to slow down. Keep up the good work and the people will come around, I promise."

"How can you be so sure?"

"because the same thing happened to me, when you stop trying to force the solution it will happen on its own."

Kara turn back to Barry, "I'm really sorry you're locked out of your world but I'm really glad you're here." Kara said.

"yeah, me too." Barry responds looking at her. A smile forms on both their faces and after a couple seconds they both blush and look away.

The two then headed off back to the DEO trying to find ways to defeat the two metahumans that they fought.

-----

Back in the DEO Barry was explaining to Kara the ear pieces he whipped up to block the sound from Silver Banshee, explaining how he used things like this before to beat the Pied Piper.

As they finished Livewires face appeared on the screens across the wall and began taunting them telling them to come to national park or that they would kill Cat Grant.

"You don't have to do this Barry this is my fight." Kara tells Barry.

"one for all and all for.... You have the three musketeers here, right?"

"And all for one"

The two heroes run out of the DEO with Barry running alongside a flying Kara, following her into the city and to the park.

As the two turn up at the park thy see Livewire tormenting the public and them running away whilst the villains turn to threatening Cat Grant instead.

"hey, Shreaky, Livewire, what do you say we step away from the nice lady, settle this like women."

Kara turns to Barry confused, "what? There's more of you then there is me', Kara smirks and turns back to the criminals.

"kill them both" Livewire tells Silver Banshee as she goes and screams at the two of them.

"What happened? Lose your voice?" Flash taunts before Livewire goes and throws electricity at the two as Kara flies up out of the way as Barry runs around it and knocks the two apart.

As Livewire gets up, she enters the electronics through a nearby lamp and uses it to climb up a nearby building, Flash runs up the side of the building to keep up and confronts her as she reforms on the roof. Barry runs trying to knock her out but instead she hits him with a large blast of electricity which knocks him down and out.

Kara on the ground goes towards Cat and brakes off her cuffs, "took you long enough" Cat says.

"Seriously?" Kara responds before Silver banshee walks up behind her and turns her around and punches her in the face with enhanced strength knocking her back and down onto the grass. Getting up Kara punches the nearby pavement, breaking off a piece of concrete which she throws at Siobhan only for her to scream causing the projectile to shatter in the air into little more than dust.

Leslie appears next to Siobhan as she does this and notices a helicopter flying by yelling, "I hate helicopters" as she throws lightning at it. Seeing this Supergirl jumps into the sky to block the lightning from colliding with the helicopter but in doing so she is knock down to the ground between the enemies and the public.

Seeing this the public races forward and surrounds her. "Yesterday you were ready to string her up and now you willing to die for her?" Livewire questions. One of the people in the crowd responds saying, "she was willing to die for us"

"What say we thin the herd" Leslie says as she powers up her hands to shoot down the crowd before nearby firemen spray water onto her, electrocuting her and the nearby Siobhan taking them both down.

The crowd responds cheering, Barry who had been standing atop a nearby building and had left Kara to take the bolt he could have caught in order to gain the publics trust back, was smiling at the scene before him before racing down to meet Kara who had just stood up with a growing smile on her face. Barry then heads off with the local police to help them set up cells to hold the two criminals whilst Kara headed back to Catco.

-----

Kara went out meeting Barry in the desert outside the city where he had brought them to earlier that day.

"You really think this is going to work?" Kara asks.
"Well fighting livewire and Silver Banshee reminded me of something we did on my earth, you and I join forces, literally, we combine your speed with my speed, if you throw me forward at your highest speed then I might just break the dimensional barrier and get back home."

"What do you mean, Like a race?" Kara answers with a challenging smirk on her face.

"Yeah, I guess, think you can keep up Girl of Steel?" Barry responds to Kara's laughter.

The two heroes walk up to get started as Kara turns to Barry. "I'm really going to miss you Barry Allen." Kara says feeling the butterflies in her stomach as she looks at his face and feeling more sorrow at him leaving then she thought she should have given she's only known him for less than 24 hours.

"I'm really going to miss you too Kara Danvers, or Kara Zor-el which is your alien name, because you're an alien which I think is very cool." Barry says facing Kara and looking into her deep blue eyes.

The two are drawn closer to each other moving in as they look into each other eyes, before they know it their lips have met as Barry reaches up and cups Kara's cheeks as she does the dame to him. The kiss seems to last for hours to the two but only a few minutes later the two break apart with flushed faces but huge smiles.

"Sorry" Barry says, "I just couldn't resist, I know I'm going away but I couldn't help but kiss the amazing, beautiful woman I ended up catching out a window this morning" Barry says rubbing the back of his neck.

Kara looks at him with a beaming smile on her face despite her embarrassment. "It's ok I feels the same way, I don't know what it is about you, but I feel more emotions with you then I've ever felt before" Kara didn't know what was happening but she knew when she kissed the man in front of her that fireworks exploded inside her and she felt a spark like no other pass between them that had nothing to do with their powers.

Barry's face lit up again with a broad grin and the two moved back in kissing once again but not for as long before pulling back and giving each other a tight hug. Despite the discomfort Barry doesn't want the hug to end but it does as Kara steps back blushing realising she wasn't managing her strength and accidentally damaged Barry's ribs.

Barry smiled regardless, "It hasn't been long since I met you but I have strong feelings for you too Kara but I'm going away and I don't know if I'll ever return so I think you should know, I'm pretty sure James Olsen also feels the same way and whilst my advice for going slow is good for superheroes it isn't for two people who really like each other" Barry struggled to say this feeling like he was giving away the chance at something he really wanted.

Kara blushed looking down at her feet but despite her reaction she found that since Barry came, and, in his presence, she hadn't had a single thought of Jimmy who had previously plagued her thoughts. She found herself feeling more for Barry then she ever had for Jimmy and didn't want to lose him, almost tearing up at the thought of her new friend, and maybe more, going away forever.

Pushing away these feelings she responded, "Yeah, maybe" before pulling the Scarlett Speedster into another tight hug before backing off and subtly wiping at her eyes and turning to face where they would run.

"Let's do this Flash"

Despite feeling similar despairing emotions Barry turns to her and smirks, "Lets see who's really faster Danvers".

The two run off and at their top speeds Barry turns to her and gives her one last smile before she reaches across and throws him forward and through the breach that had formed before them before stopping on the ground before the breach that had already closed.

Staring at the empty space a tear drips from Kara's eye, "I'll miss you Barry, I really will because I think I'm already falling for you".

Kara turns back and flies off towards her apartment where she wishes she could talk to Alex about what happened and trying to figure out what she's going to do or if there is anything to be done at all.

As Kara falls asleep on her bed in her super suit her last thought she had is that she'd try to move past him, but she'd still count the days till the Flash runs back into her life.