Kara Zor El and Barry Allen were from two different universes. Before Barry was struck by lightning, he actually lived on Earth-3. It was the lightning that brought him to Earth-1.
As children, Kara and Barry went to schools that were very close and even summer camps. Somehow they managed to become very close friends. They shared most of their darkest fears, and secrets. That was until Kara ended things.
Barry, wanted it. He wanted Kara. More than Iris. More than anyone. He wanted to get back to what he called "Kara's World".
Somehow he did it. But when he got there, she had closed off even more. The Kara Danvers he once knew wasn't herself. Then Barry heard about Supergirl. He decided to make his best impression. But that didn't go to well either as at the mention of his real name, she flew away.
The World's Finest may have had more background and romance, but saving it is key.
I do not own any of the Supergirl, Glee or CW characters in this book!