He could not remember the first time he saw her underwear. It was probably just a bra strap or something, peeking out from under her school uniform one day. Or maybe she had leaned over a little too far one day in class trying to answer a question. Ron didn't remember. It wasn't really significant; he took no notice of it the first time it happened. She was a girl, he was pubescent. That was it. He couldn't remember the first time he had tried to see her underwear. She may have been pouring over a book in the library and not paying attention to who might be watching. Or reaching a little too far for orange juice one morning at breakfast. He didn't remember. There was no earth-shattering revelation that he was attempting to glance down Hermione's shirt. He didn't particularly notice, or care, when exactly he started doing it, he was just appreciative when it happened, however infrequently.
He did however, remember the first time he held her underwear.
It was the summer before sixth year. He and Harry were in his room, lounging on their beds, flipping through various copies of Ron's Chudley Cannons fan magazines, and ignoring the pile of laundry Ron's mother had by his door for him to put away.
There was a knock on the door as Mrs. Weasley entered. "Ron, I-" Her eyes flashed over to the pile of laundry, untouched, a few feet away from her and her eyes narrowed.
"I wanted," she continued, "to let you know dinner would be ready in a few minutes and to start getting washed up. Haven't those clothes been there since this morning?"
Ron glanced guiltily at the pile. "Mum! They'll still get put away…"
"Mrs. Weasley placed her hands on her hips. "By me? I am not responsible for everything in this house, Ronald Weasely. You're going to be of age this year, and I think-" her tone now somewhat dangerous-"it is not too much to ask to shoulder a little more responsibility, even if it is for no other reason than to spare me having to go through your drawers. Dinner will be ready in about ten minutes."
With that, she left the room, and Ron, rolling his eyes at Harry, who remained seated, chuckling slightly on his cot, got up and began putting his clothing away.
"It's only laundry! And it's not like it's messing up the house or anything, it's not like anybody ever comes in here…" He stopped. "What is this?" he said, disgusted, holding up a small pair of white underwear.
"What, they're not yours?" said Harry smirking.
"Haha," said Ron. "OY! GINNY!" he yelled, sticking his head out the door.
"What?" came Ginny's response from the floor below.
"You're laundry got into my pile again!"
"So?"
"So it's yours! Come get it!"
Ginny's sigh seemed especially audible as she began making her way up the stairs.
"Wouldn't it have been just as easy to come bring it down to me?"
"No," said Ron, throwing the pair of underwear to her.
"These aren't mine," she said, tossing them back to Ron.
"Well they're too small to be Mum's!" said Ron.
"They're probably Hermione's, you dolt."
Suddenly Mrs. Weasley's voice came from the kitchen, calling them to dinner. Ginny rolled her eyes at her brother and left to go downstairs, but Ron remained in his room, the underwear still clenched in his hand.
They were Hermione's. He stared down at them. They weren't anything special, nothing shocking. They were simple, clean, white cotton underwear, with a tiny white bow at the front of the waistband.
They were Hermione's.
Harry cleared his throat awkwardly as a reminder to Ron that dinner was probably more important than examining Hermione's lingerie. Ron snapped out of his reverie and, as nonchalantly as he could, tossed Hermione's underwear back onto his bed.
As he ate, his mind kept drifting back to them, just sitting innocently on his bed. Hermione was only a few seats away from him. She kept looking at him strangely, but she was probably only reciprocating his own expression. Ron was very well aware of the fact that if that pair was upstairs, they were not currently on Hermione. That knowledge opened a whole new floodgate of curiosity as to what she was wearing, and now that he knew what she liked, his imagination was much better equipped to try and guess.
He really had meant to give them back to her. It just seemed so awkward, so daunting, to have go up to Hermione and say, "By the way, Mum accidentally dropped these knickers in my basket." The more he put it off, the more impossible it became to return them to her. And he had been so sneaky about taking them off his bed and putting them in the back of his sock drawer before Harry came back to his room after dinner. It's not that he had intended to steal them; he really hadn't. He just knew Harry would make more of the situation than it was. Besides, they were a pretty common pair. It's not like Hermione would miss them. He supposed he could have slipped them into her wash or something, but then there was the chance that Hermione would notice how long they'd been gone, so it was easier just to keep them, safely folded in the back of his sock drawer. There was something kind of nice about knowing that Hermione's underwear and Ron's socks occupied the same space.
After a while, seeing, and even occasionally feeling (when it was his turn for the wash), Hermione's underwear became less of a big deal. Living in a tent somewhat limits privacy, and things like that just… didn't matter. He never saw her in her underwear though. She was still pretty adamant about that. Harry and Ron bathed and changed alone.
Ron could remember the first time he saw her in her underwear, though it didn't really register at the time. They had just arrived at Shell Cottage, and Ron had just deposited Hermione on the bed Fleur had led him to. As soon as he set her down, she began to remove her outer clothing to gain better access to her injuries. As she peeled the blood soaked fabric away she discarded it on the floor. Ron watched dumbly, and remembered thinking it would leave a stain on the floor. Fleur began to dab what Ron could only assume was essence of dittany on Hermione's newly exposed wounds, murmuring as she worked. There was no sense of irony. She wasn't wearing simple, clean, white cotton underwear with a little white bow on the front, and Ron felt no hollow sense of humor. He had no painful revelation that this was the first time he had seen Hermione in her underwear. In fact, he was only vaguely aware that she was in her underwear. It did not reach him on the same level of consciousness as first holding her underwear did; it did not possess any significance. Being in her underwear did not make her look any less like Hermione. Like unconscious, bleeding Hermione. Ron held her hand as Fleur worked. He didn't speak. He didn't acknowledge Fleur's presence. He just stared at her. Once he was sure she was conscious and being taken care of he went down to help Harry. The next time he saw her, she was in one of Fleur's dressing gowns. Instinctively, he put his arm out for her and she leaned into him. She must have been aware of how she had spent the last few minutes in Ron's presence, but she didn't acknowledge it; it didn't seem to matter. And there was something kind of nice about that too.