Author's Notes: I've been really bad about updating here, mostly because I usually copy and paste from AO3, but that site's been so glitchy for me (or just my laptop) recently that it's been driving me up a wall. Not an excuse, of course. Luckily I've already got the next chapter of this written! I'm too fond of this light AU to let it go. Except, you know, there's always that tiny hint of angst. Cassian is a worrywart. Bonus points for bed sharing though! I love that trope, but very rarely write it myself.

A Brief Lesson in Chemistry
the sleep over

A week had passed since the party and he'd only seen Jyn once and that had been for the physics class they shared. There hadn't been time to talk because of a test and so he'd honestly been more focused on the paper in front of him than the girl beside him. By the time he managed to finish his test and lift his head, she was already gone, having sped through it. He hoped she hadn't rushed it on purpose and missed a few answers. She was smarter than that, but she was also terribly impatient.

Once or twice, he expected her to appear in his dorm like she usually did at least once a week, but she never came. He would've thought about it, but he was too busy studying for his other mid-term exams coming up. The only contact between them was a few sporadic texts. He did not tell her that he missed her because that would be sappy and admitting something that he didn't even want to admit to himself. Besides a few random gifs and memes to describe their current drowning in schoolwork, their conversations remained brief and impersonal.

Cassian really did miss her though. Kay had even pointed out that Cassian was acting more sullen than normal, although he had the decency to not hypothesize on whether it had anything to due with Jyn's absence.

Physics came again and Cassian showed up on time as usual. He watched the clock tick down until class was about to start, anxiously glancing at Jyn's empty seat, when the door burst open and the girl in question slunk into the room. He was somewhat startled to see that she was wearing his high school hoodie, his favorite one that had been suspiciously missing for a few weeks. It was larger on her, the sleeves bunched up so that only the tips of her fingers poked out and hanging midway down her thighs, but it looked cozy. He looked away, wondering if anyone noticed, but then no one here knew what small-town high school he'd graduated from.

The only person that would recognize that hoodie and knew what it meant was him.

Jyn slid into the seat next to him, looking like she was doing her best to hide in his hoodie and behind her backpack which she sat on top of her desk. Cassian opened his mouth to say something to her when the door opened again and an unfamiliar man stepped inside. He had an easy air about him that still somehow managed to command attention. Cassian shut his mouth. Whatever was up with Jyn, he'd have to find out after class.

"Good afternoon, class," the man greeted as he set his satchel on the desk up front. "Your professor unexpectedly went into early labor and is enjoying some quality time with her newborn, so I will be taking over the class for the rest of the semester. I must confess that it's been a while since I've taught such a low level of Physics so please feel free to call me out if I begin to sound ridiculous." He smiled pleasantly at them. "My name is Galen Erso, but call me whatever. I've been stuck around stuffy academics and scientists for far too long."

Cassian immediately snapped to attention. Galen Erso. He didn't know the man, but… Erso - as in Jyn Erso. The man up front had to be Jyn's father or uncle at least. Cassian tried to surreptitiously glance at Jyn, maybe catch eyes with her, but she was doing her best to avoid looking at anyone, especially him and their new professor. In fact, she was acting like she wasn't even here.

That was a terrible sign. There was no way he was going to be able to simply get an answer out of her.

The entire class, Cassian's attention was divided between the professor and Jyn, but it left him without really knowing what happened by the time the hour was up. When class was over, she all but ran out of the classroom without so much as a glance towards their new professor. For his part, he sighed as he looked sadly at the closing door and then began to pack up his things. Cassian was slower, allowing classmates to pass him, as he tried to get a better look at the man.

As if knowing that he was being watched, Galen glanced up, but Cassian ducked his head and fell into step behind a few other students to keep himself out of view. By the time he was in the hallway, Jyn was nowhere to be seen. He knew better than to text her. She either wouldn't respond or would deflect. This was clearly something very personal and, if she wanted to talk about it, she would do so in her own time. He could pry all he wanted, but that would probably just cause her to keep her distance from him as well and he definitely didn't want that.

And so he went about the rest of his day, although he couldn't help but glance at his phone. No messages from her appeared on his screen. He didn't know what he was expecting - some grand reveal, a thorough explanation when she'd never given one before about anything - but he was still frustrated. By the time he returned to his dorm, irritation and concern had built up inside him to a boiling point and he tossed his backpack on his bed hard enough that it hit the wall.

Kay peered down and then at Cassian from his perch on the top bunk. "What did that backpack do to you? Did a strap break?"

"What?" Cassian looked up, distracted, and realized that he hadn't even noticed that his dormmate was in the room. "Nothing - it did nothing."

"I'd hate to see when something does do something against you then," Kay replied before returning his comic book.

Cassian was unpacking his things with more care when a knock at the door came. The two boys glanced at each other in confusion, each silently questioning the other, and then at the door. Neither one of them were expecting a guest. Maybe it was the RA, come to check on them after the thump against the wall. Since he was already down there, Cassian went to the door, ready to apologize for the noise, but found himself surprised instead to find Jyn skulking in the doorway.

"You knocked," was the only thing Cassian could think to say.

"Yeah, well, you were already in here," Jyn pointed out, like that made any sense whatsoever. She had her arms folded across her chest. Also, she was still wearing his hoodie. "Can I come in or are you busy?"

"Kay's here," Cassian said, like that made any sense. He didn't know why he'd said it; maybe it was because she usually tended to stay away from the dorm if Kay was there. He couldn't tell if it was because she didn't like Kay or he didn't like her.

Before she could say anything, Kay climbed down from the bunk. "Oh, don't worry about me. I have to go to the library." He put his coat on and picked up an assortment of comics lying on top of the desk. "I'll be back later." He didn't say anything to Jyn as he stepped out of the dorm and she moved out of the way. Cassian scratched the back of his head. Had Kay left because of Jyn or had he really needed to go to the library? If it was the former, Cassian would have to apologize and he didn't even know what for.

Jyn lifted her chin. "So, can I come in?"

"Well, since you asked so kindly…" Cassian took a step back and she slipped inside. He shut the door and turned to watch as she moved to sit on his bed. She always chose the bed to sit, never the chair, and it always forced him to make a difficult decision on where he was supposed to sit or where she wanted him to sit. Sometimes, it felt like two very different things. Judging from her caginess earlier though, the chair seemed his best bet. She clearly wanted to see him for some reason, but she wanted her distance as well.

He sat down in the chair and tried not to watch as she fidgeted on the bed. There was so much restless energy built up inside of her. He wondered if she'd gone to swim practice. She never skipped - her coach, Gerrera, was too much of a hard ass to allow that to happen - but he didn't see her as being capable of focusing for that long. She was too wired.

Cassian really wanted to ask her what was wrong or why she had come here, but he couldn't get the words to come out of his mouth. Instead, he said, "You're wearing my hoodie."

"Hm?" The same distracted response that he'd had just a few minutes ago with Kay. Her mind was elsewhere. Jyn glanced down and her eyebrows raised, like she had just noticed that the hoodie wasn't hers. "Oh, yeah, I was cold and I-" She looked up at him, but her eyes didn't focus on him. "You can have it back."

Without warning, Jyn reached down and grabbed the hem, jerking it over her head. Along with the hoodie came most of her t-shirt underneath, exposing her stomach and most of her ribcage, and his breath hitched for a second as he gawked at the smooth skin he'd guilty daydreamed about touching. But when Cassian caught a glimpse of her black bra, he panicked and shot forward.

"No, no!" He almost touched her, but pulled his hands back at the last second. She let go and allowed it to fall back down, covering her up again. Cassian tried to put on a reassuring smile, but it probably clashed horribly with how red his face was. "You can keep it. Really, it's fine. Besides, it's, uh, cold outside."

Nice recovery, Andor, he thought sourly.

Jyn eyed him, but then nodded her head and folded her hands in her lap. He could've spent the next five minutes thinking about how it would feel to splay his hands against her bare ribcage, but Jyn said the one thing that killed any possible chances to daydream about such a dangerous thing. "Our new physics professor is my father."

"Ah," Cassian sighed, replaying the events of the class in his head, "I suspected as much." She took a breath and gazed down at her hands. The urge to switch to sitting next to her crossed his mind, but he couldn't tell if that would make her more distant or not. Much like him, she didn't like pity and he was worried any gesture of comfort might come off as such. "You don't seem happy about it."

"It's not that." Jyn huffed. "It's just that - I haven't seen him in a while. He's some important scientist or whatever. His work kept him gone from home a lot. Even after my mom's death...he just wasn't there a lot."

Cassian's hands clenched. For as long as they had been strange friends, neither one of them had talked about their family. He hadn't known that her father was a scientist or a professor nor had he known that her mother was dead. He didn't know how to respond. It didn't seem like it was the proper time to announce that his mother was also dead, along with his father, and had been for most of his life. He also didn't think she wanted him to say that he was sorry or that he understand what she was going through, mostly because he didn't. His father would never step back into his life to show up as one of his professors.

"He didn't say anything to you before coming here?" Cassian asked.

Jyn bobbed her head. "He called a few times, but I didn't answer. I guess that one's on me."

"Are you...mad at him?" Cassian would've given a lot to see his father again, but then he had very few memories left. It appeared as if Jyn had the same problem, but not because her father had passed away. Dead was very different from absent. Perhaps because it had been many years and he could barely remember the day he'd become an orphan, absent sounded a lot more painful.

"No," Jyn replied defensively, and then- "Yes, maybe. I don't know." She blew out some air. "He was a very loving and attentive father when he was there. And he would call while he was away for work. I'd spend hours waiting by the phone on the days I knew he was going to call."

In a way, Cassian could understand that. After his parents' deaths, his entire life had become one big waiting game. There was the time spent in the foster care system, then in foster homes, then bouncing between distant relatives. It didn't matter. He was always waiting for the day he would be passed on to the next person. It wasn't that he had been a disruptive or even difficult child. He just never seemed to be enough or he was too much.

Honestly, he didn't begrudge anyone for not keeping him, but it hadn't built in him a healthy sense of trusting or a desire to build connections. Kay was perhaps not only his longest friendship, but the only person to remain consistently in his life once becoming a part of it. It struck Cassian quite suddenly that while he hadn't known Jyn for nearly as long, he would've been hurt if she left. When had that happened?

"Who did you live with while he was gone?"

At this, Jyn actually laughed. "Gerrera, if you can believe it. He and my parents were old friends. It's how I got into swimming." It still shocked Cassian every time to see Gerrera and know that the mildly out-there man had almost been on the Olympic swim team. The laughter died quickly from Jyn and her face went blank. Her eyes though - her eyes were very sad. "I don't want to talk about it, to be honest."

"That's fine." Cassian was good at drawing things out of people, but he figured it was because he knew how to wait. He could be patient. He gave people time, allowed them to feel comfortable before opening it. People tended to talk more when they were comfortable. He grabbed the laptop next to him. "Want to watch a movie? Kay has a serious problem with illegal downloading, but he finds the best quality ones."

"Cassian," Jyn exclaimed in mock-incredulity, her eyes glittering, "I didn't know you broke the law so casually."

A smirk crossed his face. "What can I say? I'm a rebel."

She smiled at him and pulled her legs up on the bed, scooting so that her back was against his pillows and she was pressed against the wall, allowing him ample space beside her. He knew what that meant and it was simple, but his heart raced in his chest nonetheless. After turning off the light, he crawled in next to her and they both kicked off their shoes. She quickly found a movie that neither of them had seen and got it started.

There was no space in between them. Her side was pressed up against his, her hip and arm lined up against his. It was an awkward position, leaving them both scrunched up, and probably uncomfortable. Taking a quiet breath, Cassian squirmed until he could move his arm and then put it behind her shoulders. He did his best not to touch her, lest she think he was trying to make a move, but no contact was impossible. Only when she snuggled against him (to get a better view of the screen obviously) did he breathe and relax, allowing his arm to drape over her.

They didn't speak much during the movie, only to make a few comments and crack a joke or two. It was a decent movie, but he felt spectacularly comfortable. They ended up watching another movie without a second thought. Both of them had been studying their asses off for midterms and deserved a break. Besides, Kay didn't show back up, which meant that he was indeed at the library. He had a habit of staying there until the librarians kicked him out when he got sucked into something.

By the end of the second movie though, Jyn was drifting off. He could feel the way her head kept lolling against his chest and the way her breathing began to slow. When it was finally over, she'd fallen completely asleep. It appeared as if everything - tests, studying, practice, emotions - had worn her down. He carefully moved to put the laptop on the desk, the screen the only thing illuminating the room, but Jyn stirred anyways.

"Oh." She rubbed at her face. "Damnit, I fell asleep."

"No biggie, the bad guy died, the hero got the girl," Cassian told her.

Jyn scoffed, but there was little energy behind it. "Boring." She blinked and looked tiredly around the room. "I guess I should go."

"You could stay," Cassian found himself saying before even thinking about it. She peered up at him with a suggestive face, but didn't move away either. He cleared his throat. "I mean, you're clearly exhausted and walking tired in the cold this late at night would be...dangerous."

"Is that how you convince all the other girls to sleep with you?" Jyn asked, her voice filled with mirth.

"I don't-" Cassian snapped his mouth shut and stared down at her. She was so amused - he could see it in her eyes - but he could also tell that she was curious. Did she actually think that he wooed girls into his bed? With a roommate like Kay, that was highly unlikely and a recipe for disaster. Kay said he could be charming if he wanted to be, but Cassian just… Well, he never wanted to be. And he didn't feel very charming right now. He felt more like an idiot. "We'd just be sleeping."

"Hm, boring," Jyn said again, which was utterly frustrating because he couldn't tell if she meant it or not. Was she just teasing him again? Trying to get a rise out of him? Well, it wouldn't work. Cassian had spent a lot of his life learning how to tamper down everything and not let things get to him. She stretched in the bed, lifting her arms and touching the wall, her lithe body touching his in multiple spots. No, she could not get a reaction out of him. "You wouldn't mind?"

Cassian shook his head. "I wouldn't have offered if I did."

"And Kay?"

"He'll get over it," Cassian said. "I've spent years dealing with his insomnia. Sometimes, he acts like he's not a human that doesn't need sleep to function."

She considered her options for a moment. To be honest, she didn't look very tired anymore, but she did seem very unwilling to leave the bed. He couldn't see why. Dorm beds weren't very big or known for their comfort. Hers couldn't be much better. "Okay, but I sleep in the nude."

"Jyn," Cassian strained, at once shocked and very inappropriately turned on. She was definitely teasing him and trying to get a reaction. That one, coupled with the sudden mental picture of her naked in his bed, almost got to him. He hurried out of the bed as she laughed and flopped down on the mattress. What a terrible girl. She was the worst. Why had he thought offering her to stay the night was a good idea?

"Seriously though," Jyn continued, "do you have any shorts or boxers I could borrow? Jeans aren't exactly cozy sleepwear."

Cassian gave her a stern glower and then set to finding a pair of shorts for her. After handing them over, he turned around because he just knew that she was going to change right there. He could hear her sliding her pants off and putting the shorts on. What he was not expecting when he finally turned around was to see her magically pulling her bra off out from underneath the hoodie and dropping it on the floor next to her pants.

That was one step too far. "I'll be back. Have to go to the restroom to wash up before I can sleep." He snatched his things, ignoring the amused look on Jyn's face, and hurried out of the room. Brushing his teeth had never been so strenuous. He tried to recall the questions from his Asian Religions study guide as he changed, forcing everything out of his mind. As long as he focused on that class, he'd be able to think of nothing else.

By the time he came back to the dorm, Jyn was already curled underneath the blanket. His hoodie had joined the rest of her discarded clothes, thankfully hiding her bra. He was quiet as he set his things down, thinking that she was asleep, but then she lifted the blanket when he turned towards the bed. Trying to act as cool as possible, he slipped in beside her. Warmth immediately enveloped him, not just from the blanket but also her body. It had been quite a while since he'd shared a bed with anyone. He'd forgotten how hot it got or how little space there was.

At first, Cassian tried to give her as much space possible, but that meant lying on his side and either facing her or turning his back to her. Like usual, she made the decision for him. At first, she wriggled closer to him, so that front of her body was pressed against his. He tried not to react, but took a sharp intake of breath at the feel of her soft breasts against his chest, the heat of her breath close to his neck, the way she gripped his shirt to pull him closer. It would've been fine if she hadn't kept shifting to get comfortable, unintentionally rubbing against him.

"Is this, ah, not comfortable?" Cassian asked quietly, trying to mask the strain in his voice. They were so close, even closer now than they had been when they were dancing at the party. One of his hands found the small of her back and he almost instinctively pushed her closer. Admittedly, things were getting a little uncomfortable for him. If she didn't stop, he didn't think he'd-

No, he wasn't some stupid asshole. He wouldn't do anything. Jyn was his friend. They were friends. And he had told her that all they would be doing was sleeping. He wasn't about to be the jackass that tried to do more after being so defensive about it. Saying that he wasn't attracted to her in this moment and that he didn't want her would have been a damn lie, but he'd take it to his grave if it meant keeping his friendship with Jyn intact and not betraying her trust. This entire night had been a step in that direction and he didn't want to ruin it.

"Sorry," Jyn sighed, and she indeed did sound apologetic, "it takes me a minute to get comfortable. And it's…it's been a hot minute since I've shared a bed with someone."

"I can sympathize," Cassian told her.

Jyn moved to look up at him. Her face was close to his. It would've been very easy to move just a few inches to press his lips against hers, but he didn't move a muscle. "No girls tripping over themselves to get in bed with you?"

"I don't know who you think I am," Cassian said, "but Kay probably has more admirers than me."

"You'd be surprised," Jyn teased. "Half the girls on the swim team gush about you and keep pestering me to invite you to a meet or one of the swim parties."

Cassian had no idea what to think about that. The idea of any girls talking about him, of all people, seemed absurd. Girls talked about guys like Han Solo, someone dangerous and tempting, or like Kes, who was a genuinely good guy. Cassian on the other hand? No, he wasn't what he would consider fantasy material. Jyn had to be pulling his leg because he couldn't see it any other way.

"That's nice of them and all, but I don't want to share a bed with any of them," Cassian said. He hadn't meant it as an insult, but the implication seemed too obvious after he'd said it. He didn't want to share a bed with any of the girls on her team, though they were probably plenty attractive, but he was more than willing to share a bed with her and was actively doing so.

A very soft smile appeared on Jyn's face, unlike one that he had ever seen. It was almost...shy. She ducked her head and then turned around so that her back was to him but she wiggled again so that she was pressed up against him, allowing him to spoon her. Doing what felt the most natural, he draped his arm over her and she hummed pleasantly. He grinned nervously in her hair.

After that, nothing else needed to be said. They were just two friends sharing a bed to get some sleep, but it felt like so much more than that. He did want to kiss her and he did want to hold her tighter, but this felt good too, much like when she had held his hand in front of the bonfire at the party. Something quiet and intimate that felt bigger and more important than anything else. She was opening herself up to him, allowing herself to be vulnerable. Perhaps she too would've been hurt if he walked out of her life.

It wasn't long before both of them fell asleep. And if Kay had anything to say about returning to their dorm to find Cassian and Jyn cuddling, then for once, he didn't say a word.