I don't own the trio. Obviously.
She had always been their bookworm, their go-to. She knew everything there was to know about anything, and though he and Harry blundered their way through every homework assignment, she marched through a clear path of knowledge that she cut herself. She was brilliant and everyone knew it, but he and Harry were of the privileged two who were allowed to walk alongside her now and again.
He didn't know how privileged though.
Hermione practically had a magic all her own when she put her mind to something. Harry once said that it was almost like a super-power, which sounded like a Muggle thing but made some sense to Ron (unlike most Muggle things Harry and Hermione told him about). Whatever it was, Hermione had it, and she had it by the bucketload. And Ron? Not so much. He knew he wasn't the smartest kid around—being friends with Hermione Granger will have that affect—but he wasn't a complete idiot. He was used to the average middle ground, and it helped that Harry was stuck right there with him. Hey, if the Boy Who Lived couldn't figure out what the bloody hell a blast-ended skrewt wanted to eat, then Ron had no problem admitting he was clueless too.
Hermione could have figured it out if she wanted to though. She figured out Snape's potion riddle during first year, she made Polyjuice—and made it right—when they were second years, and she spent their entire third year traveling through time with skill most adults couldn't grasp while keeping it a secret even from he and Harry.
She was their bookworm, the caterpillar that just keeps chowing down on the ever-present leaves of knowledge.
The thing with caterpillars, though, is they don't stay caterpillars forever.
During their fourth year things got real serious. For the first time in his life, Ron felt the searing pain of jealousy and he didn't even know what it was. He hated Krum, but still worshipped him as a Quidditch god. Hermione was right—why did he care that she was spending time with that oaf? Hermione was his best friend, he wanted her to be happy, and if that foreign sack of rocks made her happy, that was good…right?
And then the Yule Ball happened…
Before, she was their bookworm, their diligent caterpillar. She devoured knowledge like her life depended on it. She was the brightest witch anyone knew, but in the end she was still just Hermione. She had big, bushy hair. Her nose was often smudged with ink or with the dust of her textbooks. She wore the same sweater and skirt as every other girl at Hogwarts, and put no effort whatsoever into her looks. Every last ounce of her energy went into learning, which while highly useful was not exactly attractive.
She was a caterpillar, and in their fourth year she crawled into her cocoon. Harry may not have noticed it, especially since he and Ron were fighting through most of it, but Hermione was withdrawn. She started changing her hairstyle. She began wearing a tiny bit of make-up. Every so often Ron would even catch the scent of perfume when she passed him, rather than her usual shampoo and parchment scent. She was, quietly and subtly, changing. It wasn't obvious to anyone until the Yule Ball.
Then, like a butterfly, she emerged. No woman had ever looked so beautiful as she did to Ron that night. This was not the Hermione who had helped him write his potions essay last week. She had changed, gone through an entire metamorphosis. After that, she was never just a caterpillar anymore. Every time Ron looked at her he saw this beautiful, subtle butterfly. Through Krum, through Lavender… Hermione was never just Hermione again.
She wasn't a caterpillar after all. She was a butterfly. His butterfly. All Ron could ever hope was that he would be lucky enough to catch her one day. Even though Harry said it was obvious—hell, even though Fred and George said it was obvious—she would always elude him.
Ron was never good enough for her. She was so beautiful, so smart… he could never measure up to such a butterfly. But he chased her anyway, and one day, maybe, he would catch her….