The Crisis on Earth X crossover was pretty light on moments between Kara and Barry, but I decided to play around with it anyway. This is a short retrospective of their moments at the end of Supergirl 1x18 (Worlds' Finest) and during the wedding rehearsal in Supergirl 3x08 (Crisis on Earth X, Part I), with a little addition to each of the scenes.

As always, all characters belong to DC Comics and the CW, and this is written purely for fun. Thanks for reading. I appreciate it.

…

"I'm gonna miss you, Barry Allen."

"I'm really gonna miss you too, Kara Danvers," Barry replied. "Or Kara Zor-El, which is your alien name, 'cause you're an alien, which I think is very cool," he continued, gushing. Kara burst out laughing, her nose scrunched up in happiness.

Standing there with this amazing alien, this amazing woman, in front of him, Barry couldn't help the small twinge of regret he felt at having to say goodbye to Kara. It'd all started with him catching who he thought was someone helpless falling from the top of a building. A multiverse explanation, a tour of a secret government facility, and two metahuman threats later, and now he couldn't imagine his life without having met the Girl of Steel. Unable to maintain his relationship with Patty because of his identity as the Flash, and uncertain if Iris would ever reciprocate his feelings, Barry now found himself with someone who just understood both the joy and the responsibility of their powers, and it was a connection he wished he could explore further with her.

Then again, was there really any point? It's not like he had her attention, anyway. "I think James Olsen thinks so, too," he added, following up his previous comment.

Laughing nervously, Kara stammered, "What makes you say that?"

He understood the appeal, even without knowing James personally. Tall, handsome, and according to Winn, an award-winning photojournalist and close confidant of Kara's apparently more famous cousin, Superman. He was already vetted as far as the kind of person he was by Kara's own family, and most importantly, it was abundantly clear how much James cared about her.

Barry? Well, he was the fastest man alive…on his Earth. Here, Kara hadn't even heard of him before today, and maybe after today he'd never be in her thoughts again. His heart grew a little heavier at that sobering thought. Still, it was no reason for him to hold back on nudging her towards something she seemed to want.

"You remember before when I told you to take things slow? It's good advice, for a superhero," he told Kara. "Lousy advice for two people who really like each other. Maybe it's time to speed things up."

Kara nodded thoughtfully, though Barry thought she still looked a little unsure. "Maybe."

Barry leaned in to give Kara one last hug goodbye, which she eagerly returned, throwing her arms out wide as another smile split her face. In spite of his feelings, which he could admit were very "spur of the moment," he hoped she would think about what he said about James, as it didn't take much time to recognize that Kara Danvers was a special person and deserved all the happiness in the world. As he held her close, however, a sudden rush of daring overcame him as he realized the implications of him possibly never seeing her again. He might not get another chance anyway.

Ah, what the hell.

"But," he said, pulling away, "as good a guy as James seems, I am running into a breach in the fabric of space and time, about to be an entire dimension away from you, so…"

She gave a confused smile and raised her eyebrow. "Barry, what're you…oh."

Before he could lose his nerve, Barry leaned forward slowly and gave her a small, chaste kiss on her cheek. When he pulled back, a flirty grin on his face, he was gratified to see a little smile and, if he wasn't mistaken, a very human blush on hers. "It's not every day a guy has a chance to kiss a cute alien," he teased.

Kara giggled and momentarily turned her head away, whether out of shyness or because she was embarrassed for Barry and his forwardness, he couldn't tell. When she turned back, however, her flirty grin mirrored his.

"Watch it, Allen," she warned, wagging a finger at him in mock seriousness. "Don't make me come after you through that breach."

Barry laughed, and Kara laughed with him. He wasn't sure he'd ever see the Girl of Steel again, but he knew as long as they both lived, even in different dimensions, they'd be rooting for each other. In the end, maybe that'd have to be enough.

…

"You're doing it again."

"Doing what?"

"Trying to stay above it all, so that you'll hurt less."

Kara bristled briefly. "I'm not—," she began, before looking down and actually focusing on where she was. Sure enough, she had drifted almost unknowingly to the empty upstairs section of CC Jitters, quietly watching everyone interacting below as she stood alone.

"See?" Alex prodded gently, leaning against the railing next to her. "J'onn told me you were doing the same thing back in National City, when the Girl of Steel statue was unveiled. Standing alone on top of a building. I believe his precise words were that you were 'courting emptiness.'"

Kara rolled her eyes. "J'onn's being too dramatic. I was trying to concentrate on security." When Alex continued to look concerned, Kara tried to reassure her. "I just needed a little break from everyone. Given our personal problems, maybe a wedding wasn't the best idea."

"You can say that again," Alex chuckled humorlessly. "I don't even know Barry and Iris, and even I can tell they're perfectly in love."

A tiny part of Kara twinged at that observation, but she said nothing as she glanced at the happy bride and groom below. Alex sighed, looking down at the open bar directly under them. "Well, I think I see a bottle of scotch with my name on it. If I'm going to be miserable, I may as well get drunk on someone else's tab." With that, Alex turned and began descending the stairs. "Come back down soon, okay?"

"I will," Kara called out. Moments later, she spotted Alex reappear underneath, helping herself to shot after shot of alcohol.

What was I thinking?

It'd seemed like a proactive idea at the time, but now Kara could not for the life of her remember why she had thought coming to this wedding would help Alex or her feel better about their current romantic situations. Coming here didn't change the fact that Mon-El was now seven years older and married to someone else. Coming here didn't change the fact that, in spite of the strides she had made to move on, she still felt she had so far to go. She'd hoped for distraction but instead just felt more confusion than ever.

That confusion also certainly wasn't helped by the matter of one Barry Allen.

If Mon-El was shaping up to be her "star-crossed" story, Barry would always be her "what if" story. The instant, magnetic bond they had formed the day he accidentally arrived on her Earth had left a lasting impression on her, and to this day she was astounded at how immediate their connection had been. The rush of finding someone new who not only understood and accepted the burden of protecting the weak but also still reveled in the joy of superpowers had been a powerful sensation that she had never really found again with anyone else.

Had they existed in the same dimension, she would've been more than interested in seeing where that bond could have taken them, but Barry, of course, lived on a different Earth, and she was perhaps still too caught up in James in the moment to fully appreciate what could have been. By the time they'd managed to bridge their different worlds, the two of them simply weren't available at the same time, and now Barry was on the cusp of his wedding day.

She could honestly say to herself that she was happy for Barry, though, especially since he was marrying Iris. An accomplished reporter for Central City Picture News, the de facto leader of Team Flash's operations in Central City, radiantly beautiful, and a genuinely kind and sweet person, Iris was everything Barry deserved. Obviously, it helped that she was also Barry's dream girl from the ripe old age of eleven.

How could Kara possibly compete with that anyway?

On some level, Kara knew these thoughts about Barry were likely intermeshed with the general sensations of being at a wedding and her confused attempts to move on from Mon-El. Still, she couldn't help feeling a bit wistful at a door that now seemed permanently shut. At the end of the day, she supposed it was yet another thing from which she'd have to learn to move on. She was Supergirl, after all. These human joys simply may not be meant for her.

"Hey."

Kara quietly chuckled to herself at Barry's streak of impeccable timing. I wonder if he'd still try to catch me if I fell over the railing. Rearranging her face to reflect the happiness appropriate for the occasion, she turned to the beaming grin of the fastest man alive as he climbed the stairs to join her.

"Hey," she replied, smiling.

...

Author's notes: Direct dialogue is taken from Supergirl 1x18 (Worlds' Finest) and Supergirl 3x08 (Crisis on Earth X, Part I).