A/N: so this is based on an AU prompt i saw on tumblr: "found your number in a library book AU". i thought it would be cute with this pairing! this is going to be very light and sweet, so if you're looking for angst...it's not here. i just want my kids to be happy ;-;. anyway, thank you for reading! i hope you enjoy! this is not beta'd but i did proofread to check for continuity and grammar errors. also, i refer to Ruka with her pronouns because in this fic (and in my opinion, in canon) she is transgender. if you don't like that, leave now. i don't want mindless arguing in the reviews, thanks.

Libraries were always a place of quiet solace after stressful days. Even if she didn't check out a book, Kurisu liked to stroll the aisles and look at all the spines, neatly placed in rows, the titles in Japanese. It had taken a few weeks to switch to reading Japanese since she arrived for the summer. Thankfully she had settled into it, but she still thought in English-hell, English words slipped into her speech at times. She hoped that would diminish soon. It made her sound strange when she was speaking in a professional setting, like in the labs.

One book caught her eye, sticking slightly out among the others. "The Theory and Science of Time Travel", boasted the spine. She picked it up and flipped through it. She never found the theory of time travel to have a very strong foundation, but she tried to have an open mind nonetheless. She stuck the book under her arm and sat down at a desk, diving into the book. By the first few chapters, she could tell she liked the book, but the sun was setting and she needed to get dinner and some sleep. She used her student card to check out the book, threw it in her purse, and went in search of a sushi shop.

Kurisu ate while she read, reaching about halfway through the book before flipping to the back to see who else had checked out the book in the past. On the last page, someone had written something.

Mad scientist HOUOUIN KYOUMA was here!

Beneath the message was a phone number. She raised an eyebrow. Not many others had checked out the book. At least, no one who had made their mark so much as "Kyouma" had. A curiosity nagged at her. He was practically asking people to call him, for whatever reason. Then again, he was a self-proclaimed (she assumed) "mad scientist", so she could've been getting into something that she couldn't get out of.

She sighed and decided against it...for tonight. She set her alarm for her early lecture and put the book on the nightstand. She tried to push the unbearable curiosity about Hououin Kyouma out of her mind.

She got back to her hotel in the afternoon after classes. Lecture days always felt longer, even if it was a short lecture. She wanted to get into the science, see it, talk about it herself, feel it if she could. She wanted to be staring it in the eye, not listening to someone else talk about it. Still, she was feeling restless and a bit stir crazy at this point. She didn't want to go back to the library or the labs...maybe she'd just walk along the streets of the city for awhile.

"Are you going to the festival tonight, Okarin?"

"What? Oh, I guess I forgot about it. Probably not. Maybe I'll go to bed early."

Mayuri laughed, melodic and sweet. "Yeah, right, Okarin. C'mon, you can't stay inside all day! We haven't gone to the festival together since we were little! Do you have homework?"

"Homework? No, I didn't have class today."

"Did you not go?" Damn, Mayuri knew him too well. Still, she wasn't exactly right.

"No, I really didn't have class."

"Alright! Mayushi just wants you to get good grades," he wasn't looking at her, but he could hear her smile. "When's your next class?"

"Two days from now. Another lab."

"Oh, good! You like those labs, right?"

He nodded. "Mm, they're not too bad. I get stuck with insufferable partners at times. But there are some interesting people...there's this one girl, I don't know her name-"

Mayuri jumped at the opportunity. "Ooh! Okarin is in looove!"

"I said nothing of the sort! You didn't even let me finish. All I was going to say is that she seems very interesting. She always has something to add to the discussions...however, she's got a temper more fiery than her hair."

"Ohh, a smart girl!"

"Smart indeed, if quick to jump at you."

"Have you talked to her?"

"Yes, but we never exchanged names. It was actually an argument…"

She tsked, tsked him. "Okarin. You ought to be nicer!"

Okabe turned his computer chair around and looked at Mayuri. "I should," he said honestly.

"Try to make up with her."

"I will. I don't know if she holds grudges."

"Just try it! Oh, can we please go to the festival tonight? Ruka will be there…she got a new kimono and everything, and she looks beautiful!"

Okabe agreed that Ruka was beautiful; something about him-oh-her was like a delicate flower, despite his-damn-HER...er, biological system? He was trying to get better with that. He had made some pretty asshole-ish comments in the past that had really upset her and Mayuri, and after some searching around the internet and taking time to understand Ruka and that part of her, he felt bad for what he had said. She was perhaps too forgiving of him. He pulled himself away from thoughts of her and looked at Mayuri again. "Sure, I'll go to the festival. It's been awhile since I've seen the fireworks up close."

She nearly squealed. "Yay! Can I run home and put on my kimono?"

"Sure. Try and get back before it gets dark."

She bounded out of her seat, barely saying "bye!" before bursting out the door. He chuckled and leaned back in his chair, wondering if he should put on something a little more nice for the festival as well.

His phone rang, and he arched an eyebrow, wondering who it could possibly be. Maybe Daru? When he checked, it was an unknown number. Cautiously, he answered. "Yes…?"

There was silence on the other end for a few seconds, and his finger hovered above the end call button. "Er, this is kinda weird, but I...found your phone number in a book." This girl-he assumed it was a girl-had a very familiar voice, but he couldn't quite place it…

"A book? You mean, the phone book?"

"No, no...you wrote it in a book."

"I...what? Are you okay?"

"Don't patronize me!" she said suddenly, and he nearly gasped. That girl in his lab! It sounded just like her! "Anyway, maybe I did get the wrong number. All I know is some weirdo wrote his name and number in a book I checked out in the library."

"You shouldn't go around just calling weird numbers."

She groaned. "I have no idea what your deal is, but I'm hanging up."

"Suit yourself," he hung up. What a strange phone call.

Then it dawned on him. Ah, damn, he did write his number in a book about time travel, at the beginning of the first year of college. Definitely not the smartest move. Then again, it was a book about time travel, not exactly the biggest interest among college students, even science students like himself. She must have checked the book out and seen his scribbles.

Before he could dwell on it for too much longer, Mayuri returned excitedly. "Okarin, it's almost dusk!" she was wearing a violet kimono patterned with cherry blossoms. She had even tied her short hair up. He smiled softly.

"You look nice, Mayuri. Is that a new kimono?"

"Yes!" she grinned, swinging the sleeves a little. "Isn't it pretty? I like having special things like this, it makes it more fun when you get to wear them...you should dress nice, too, Okarin."

"I don't have much in the way of formal clothing. I'll put on a nice jacket or something."

"That would be nice! Now hurry up, I want to get there right at dusk."

Okabe went to his bedroom to grab his seldom-used peacoat from the closet. It was probably too warm for a peacoat, being that it was June, but summer nights always had a chill in the air. He stepped out of his room, Mayuri waiting just a bit impatiently by the door. "Oh, you look nice, too!"

Compliments like that didn't usually affect him (to be fair, he didn't get them often) but Mayuri was so sweet and genuine all the time he couldn't help but smile in thanks. "Ah, look who's talking, my lady," she giggled, and they ventured out into the city.

"I didn't know you could be a mad scientist and a gentleman!"

"People like me are quite versatile."

Kurisu found herself in the middle of the festival, more by accident than anything else. She felt a bit underdressed with all the beautiful kimonos around her, but she tried not to think about it. Everyone seemed wrapped up in the excitement, crowding booths that sold food and goodies, excitedly greeting their friends when they saw them from yards away. She wandered aimlessly, hoping to maybe see some acquaintances from the college.

Many people had situated themselves at the top of the hill to watch the fireworks. She found a spot in the grass next to a small group of people. One of them was a shy looking girl, who smiled in her direction. "Hi," Kurisu offered, scooting a little closer.

"Hi," she said quietly. "Here to see the fireworks?"

She nodded. "I've never seen them before. Not in Japan at least."

"They're really cool!" her smile grew. "Did you move here?"

She nodded. "Well, I'm really just here to take a summer class at the university. But yeah, I moved from America."

The girl's eyes seemed to sparkle. "Wow, that's a long way."

Kurisu chuckled into her palm. She found this girl charming and cute; hopefully this would lead to a friendship. She was embarrassed about

her lack of friends she had made in Japan, especially since she still had the rest of the summer to stay. "It is. But I was born here, so I guess it's like a second home, in a way. Well, a second home I didn't visit often…."

"Do you like it here?"

"I do," she said honestly. "It's taken some adjusting. I'm pretty occupied with school most of the time."

Their conversation was interrupted when another girl came up to them. "Ruka! I got us some snacks! Oh, who's this?"

"Makise Kurisu," she filled in the blank, reaching out a hand at first, then pulling it away, forgetting that was uncommon in Japan. "Sorry. I forgot you don't shake hands here."

"She's from America," Ruka (she assumed that was her name) said.

"Ooh, cool! I'm Mayushi, nice to meet you!"

"Nice to meet you, too," she said. "Have you been to this festival before?"

"I try to go every year! If I can't, I just watch the fireworks from Okarin's window," Mayushi giggled.

"Okarin?" Kurisu tilted her head.

"He's my friend! He's getting us food right now, I think," she looked behind her. "Oh, there he is! Okarin!" she waved.

She furrowed her brow as he came closer. He looked familiar, like a guy from her school...still, a lot of college guys had that lanky, stubbly sort of look. Still, she swore she had seen him before. Then again, it had been a pretty strange day what with the phone call and all, she was probably just overthinking. Right?

"I found chicken tenders," he said. Mayushi nearly squealed and Ruka just chuckled. "Oh, who's...this?" he looked her in the eye, and she studied his face unabashedly. He sounded familiar, certainly. "Looking for something?"

"Do I know you?"

"I doubt it," he replied. "Then again….where do you go to school?"

"Just outside of here, in Tokyo."

"Ah ha!" he said loudly, startling her. "I knew I saw you around."

"So you must be...Okarin?" she said, going off of what Mayushi had said.

His nose crinkled. "Hououin Kyouma."

"Hey! It's you!" she exclaimed, and this time he was the one confused and startled. "You wrote your name in that book! Mad scientist!"

"That was you on the phone then?"

"Yeah, I tried to explain myself but you wouldn't let me get two words in."

"I'm lost," Mayushi frowned. Ruka nodded in agreement.

"While you were out, she found my number I had written in a book and called me."

Mayushi gave him an odd look. "You're silly sometimes, Okarin."

"It was awhile ago, I don't know how she found it."

She crossed her arms. "I have a name, you know. Kurisu."

"Ah, yes, American genius girl!" he said.

"Wait, how do you know that?"

"There's talk about you around the college. Lots of big words, 'prodigy' is one."

She bit the inside of her cheek. "Oh. You heard it from them, not me. I don't go around saying stuff like that about myself."

"It's a novelty to have someone from America at our school, let alone someone with such a big name."

She shrugged awkwardly. "I mean, I was born here, I've just spent more time in the states lately."

"So you speak English, too?" Ruka asked with wide eyes. "Wow!"

She laughed. "Yeah, it's pretty easy to switch from one to the other if I need to nowadays."

"So you and Okarin have classes together then!" Mayushi said.

"I think we have a lab together. I only take two classes during the summer, and one's a lab," she said.

"And I only have to take the lab. So we must have that together," Okabe concluded.

She crossed her arms. "Yes, now that I think of it, I've heard your loud voice in those labs. You tried to tell how to write my lab report when you were completely wrong and didn't even know what I was writing about," she narrowed her eyes.

He grumbled. "Yes, yes, we got off on the wrong foot, I suppose."

"You think? But I guess I won't hold it against you…" she frowned, but there was a teasing glint in her eyes. "How did you girls get stuck with this guy?" she asked Mayushi and Ruka.

Mayushi giggled. "I'm his hostage, actually!"

Kurisu's stomach went cold. "Excuse me?"

"Mayuri," Ruka said warningly. "She doesn't mean it like you think!"

Kurisu sighed skeptically. "What does that mean?"

"W-we've been friends since we were very young," Okabe said quickly. "It's a...long story! Don't think I'm some sort of creep."

"I think a lot of things about you...but not that you're a creep. Yet," she narrowed her eyes as if in warning. "And Ruka, how do you know Okabe?"

"Kyouma," he said, but she ignored him.

"I met him through Mayuri," she said in her soft voice. "She took me to his lab once and I guess we became friends," she looked at him hopefully, hoping she was right, and he nodded in confirmation.

"Lab?"

"That's what we call the apartment! The Future Gadget Lab!" Mayuri exclaimed, with arm flourishes to go along. "So far we haven't really invented anything…"

"Excuse me, we have a variety of gadgets," Okabe intervened.

"Oh, yeah! Like the vacuum, er, I mean, Future Gadget 002," she said.

Kurisu laughed into her palm. "God...you all are the most intriguing people I've met in Japan so far."

"Oh, yay, it's always good to make new friends!" Mayuri said, and Ruka nodded in agreement before looking up to the darkening sky.

"Hey, the fireworks are about to start," she said.

A hush fell over the crowd, everyone looking up eagerly. Mayuri huddled close to Okabe, watching with wide eyes. The fireworks lasted almost five minutes, a multitude of bright colors exploding across the sky. They reminded Kurisu of going to Fourth of July celebrations in America when she was young.

Once the festivities were over, the trio and Kurisu began walking back to the apart (or the Future Gadget Lab, whatever). "Summer labs are only for a little while longer," Okabe commented. "Will I see you again after, or are you going back to America?"

"I'm staying for the whole summer," she said.

"Well, we have each other's phone numbers, now, don't we?"

She nodded. "You're lucky no one else checked that book out, you could've ended up with a lot of weird people calling you."

He rolled his eyes. "You could've just not called the number." She opened her mouth to retort, but she found that she couldn't. He had gotten her. He laughed loudly, almost maniacally. It echoed through the street. "I've outsmarted American genius girl, hmm?"

"Oh, shut up, you're toeing the line here, Okabe."

"You just met," Mayuri said softly. "Don't fight."

She sighed. It was hard to deny sweet Mayuri. "Sorry, sweetie."

"Be nice, Okarin," she gently scolded him, then turned to Kurisu. "Come back to the lab sometime!"

"I will. Thanks for spending the night with me," she said. "See you in the labs?" she looked to Okabe.

"Indeed. It was nice meeting you...Christina."

Her brow furrowed. "There's no -Tina?"

"I found it fitting," and with that, the three of them climbed the steps to their apartment. Ruka, shy as she was, turned and gave Kurisu a wave and a smile before running after them.

12:01 AM

It was nice properly meeting you, genius girl.

12:03 AM

Oh my god, why aren't you asleep?

12:05

What are you, my mother?

12:06

Go to sleep

12:09

Oh yeah, it was nice to meet you, too. ^~^

A/N: thank you for reading! comments appreciated! xoxo