Lexa's ninth birthday party was not exactly going as planned.

It was supposed to be simple. They were supposed to have the party at home, with decorations hanging from the ceiling and the swimming pool set up in the backyard. They had stored popsicles in the freezer and it would be nice, like every year, with not too many people invited and the barbecue set up for later.

Unfortunately, this morning the house had been a chaotic mess of dirty footprints and a portable radio that blared pop music to cover the noise of an electric drill. It had been like that for a while now. The slow working builders that should have completed their job days ago, still hadn't finished renovating the bathroom. It was noisy and unsettling, and didn't even feel like the familiar environment of home with all the strange, bulky men around that smelled of cigarettes and always had mud under their shoes.

So at the last minute they had decided to have Lexa's birthday party in the park instead, which really wouldn't have been that much of an issue if it wasn't a scorching hot summer day that burned any skin without sunscreen and made Lexa's mother tell them every fifteen minutes to drink enough water.

But the sun was shining and Lexa liked being outside, so that was okay.

There was more, however. The birthday cake they had ordered – it was going to be white and purple and have sprinkles of chocolate on top – had accidentally been replaced with a plain, whitish-yellow banana cake.

"We're terribly sorry about the mix-up, ma'am," the employee on the phone had said when Lexa's mother, full of dismay, called the bakery in complaint after they opened the box to be met with the wrong cake. "I can offer you a ten dollar discount on the next order?"

Lexa had swallowed her disappointment. She had wanted strawberry or vanilla – anything other than banana, really – but her friends didn't seem to mind. They had excitedly reached for the plastic sporks that were laid out on the picnic table and had grinned at her through mouthfuls of banana cake, and Lexa realized it wasn't that big of a deal.

She could have strawberry-vanilla cake some other day.

But her mom had been visibly upset about the cake mix-up – a disappointment on her daughter's birthday for which she held herself responsible. She had been pacing back and forth in the shade of a nearby tree, phone to her ear and a frown on her face as she argued with the bakery employee. So Lexa had gone up to her, a nauseating feeling in her chest because she never meant for her birthday party to cause all these troubles.

"Mom." Lexa had tugged on her mother's free hand to get her attention and the woman had fallen quiet, ignoring the voice on the other end of the line. "Mom. It's okay. I'm having fun."

Her mother's face had softened and she had kissed Lexa on her forehead, telling her to go back to the others.

And it was okay.

Everything had gradually returned to its easiness under the sun with lemonade in plastic cups and bright laughter as they played games of tag and hide and seek, and for a moment it seemed like everything else would go smoothly today.

Until the bouncy castle arrived.

"Wow," Luna gasped. "It's so pretty."

The castle had risen to its full form, the air-machine humming to keep it upright, and Lexa couldn't help but agree. It was colorful and had towers with little flags at the top and an entrance that looked like a drawbridge.

And this, she decided, definitely made up for the birthday cake incident.

She glanced over her shoulder to see her mother talking to someone else, probably one of the other parents, in the shade of the tree line. Her mom caught her eye, gave her a smile and an encouraging wave, and Lexa's heart bubbled with joy.

This morning, while her father was getting ready to leave for work, it had been a mumbled idea between her parents. He had shrugged at the idea of moving the party to the park and said, "Would be enough room for a bouncy castle."

But it had been mumbled and half the things her father said were jokes that Lexa didn't understand, so she didn't think he was being serious. But the castle was really here, overlooking the lake like a colorful, jumpy, medieval fort. So caught up in the grandness of it all, she barely noticed anything else.

"Lexa?"

"Hm?"

Lincoln frowned in confusion next to her. "Did you invite them too?"

To her surprise, another group of children were already climbing into the bouncy house, kicking off their shoes at the entrance.

"No," Lexa answered quietly. She did not invite them, but the unfamiliar kids sure seemed to think otherwise. They were screaming and laughing and pushing each other into the inflatable walls, jumping around like they owned the place.

"What do we do?" Luna asked, nibbling her lower lip in worry as she watched the other group of children who, by the look of their colorfully striped party hats, were having their own party.

"They're taking our castle," Anya said, narrowing her eyes. She balled her fists, an angry color spreading over her cheeks. "There's only one thing we can do: take it back."

Of course Luna grinned and nodded in agreement, eagerly stepping forward to join Anya on this mission.

"No," Lexa said, grasping Anya's arm to stop her. "Wait. I will go talk to them."

Perhaps they only listened to her because it was her birthday, but Lexa was glad when they huffed their reluctant agreement. Anya rolled her eyes at the boring solution, but at least her fists unclenched.

There had to be some other way to resolve this, Lexa thought. Maybe it was just another mix-up. She didn't like the idea of sharing the bouncy castle with a group of strange, rowdy children, but maybe once they understood it was here for Lexa's birthday and not just as a public playground, they would leave.

"What if they don't want to give it up?" Luna asked, grumpily kicking the grass.

The thought made Lexa nervous, but she raised her chin to make herself look proud. It was supposed to be their castle, after all.

"Then we'll take it."

Lexa approached the bouncy house with a shaky feeling in her legs. But knowing that her friends were counting on her, she squared her shoulders and didn't let the pile of unfamiliar shoes outside the castle entrance scare her off.

She deftly kicked off her own sneakers and climbed atop the inflatable drawbridge. But before Lexa could make her way inside, she was met by a confident looking girl with dark brown hair, standing in the opening, swaying along with the bouncy movement of the castle.

"Excuse me." The young girl cocked an eyebrow and crossed her arms with a challenge. "Who are you?"

She hesitated. "I'm Lexa."

"Lexa. And how do you know Clarke? Because I am her best friend and I don't know you."

"I don't know her," Lexa stammered. "Is this your party?"

"No, it's Clarke's." The girl bit her lip and shrugged, still blocking the castle's entrance. "But it's kind of mine because Clarke is my friend, so."

"Oh." Lexa frowned, trying to understand. "Can I talk to Clarke maybe?"

"Nope," the girl said, grinning. "You can only talk to me. And Octavia. Because we are the bouncers."

The bouncy castle had bouncers. Lexa wasn't sure what that meant, but it sounded official. There seemed to be many things she didn't understand yet and she wondered who should've been her bouncers. Or was everyone playing inside the bouncy house automatically a bouncer?

This all seemed very confusing.

"Do you mean, like…a guard?"

The girl stared at her, arms still crossed. "Yeah. Duh. I mean like a guard who also gets to play inside with the others who were invited."

Lexa clenched her jaw. None of this seemed fair, because these kids hadn't been invited at all. She was about to tell the strange girl exactly that, when they were interrupted by the song of an approaching ice-cream truck. All the kids in the castle seemed to storm out at once, stumbling onto the drawbridge.

"We're going to get ice-cream, Raven," one of them said, her dark hair tied into braids and a colorful butterfly painted on her face.

The bouncer (Raven) seemed to forget all about Lexa being an uninvited guest to the party. She let herself be tugged along by her butterfly face-painted friend and slipped off the drawbridge, neither of them bothering to put on their shoes before running off.

Lexa watched them, a little perplexed by this sudden end to their conversation. She liked ice-cream as well, of course, but would never ruin her socks with grass stains for it. (Or leave the spot she was supposed to guard, for that matter.)

She turned back around and found a pair of curious eyes watching her.

Another girl had stayed behind, not following after her two ice-cream crazed friends like Lexa expected. She had shiny blonde hair and rosy cheeks that still radiated excitement from jumping around in the bouncy castle, and Lexa forgot to breathe for a moment.

The unfamiliar girl cocked her head. "Hello."

"Hi." The sun shining down on them suddenly felt very warm and Lexa felt her hands get clammy, like summer sticking to her palms. She shifted on her feet. "Don't you want ice cream?"

The girl's eyes narrowed almost playfully. Ignoring Lexa's question, she asked, "What's your name?"

It made Lexa forget what she was doing there in the first place, the invasion of the castle being pushed to the back of her mind, because this girl wanted to know her name. And maybe the girl hadn't heard Lexa before, so maybe she should speak up a little – why was her voice suddenly getting caught halfway in her throat?

"It's Lexa."

"Okay," the girl grinned. She took hold of Lexa's hand with her own, casually, easily. "Come on."

She tugged them onto the grass and away from the castle. (And neither of them remembered to put on their shoes, but that didn't really seem to matter.)

The girl's hand was still firmly in her own and Lexa was starting to worry about the stickiness of her palm, when she realized they were heading towards the shade. There, her mom still sat at one of the picnic tables, talking with the same woman as before.

"Mom," the girl next to Lexa called out as they walked towards them. "Do we have any ice-cream left?"

"Check the cooler, honey," the girl's apparent mother called back.

Their parents smiled at them before Lexa was tugged away, the girl rushing them towards a picnic table further on. A dozen backpacks and shoes and half empty juice boxes were spread around it, as if marking the territory.

The girl didn't hesitate to open a blue cooler box, finally releasing Lexa's hand to reach inside.

"Do you want strawberry, or..." She frowned at the packages stuffed inside the cooler. "I think it's chocolate or something."

"Oh." Lexa licked her lips at the thought of something cold. Her cheeks felt too warm. "Strawberry is good."

With a wide grin that undoubtedly meant she had made the right choice, the girl handed her one of the ice creams and sat down at the picnic table, legs dangling back and forth. Lexa sat down next to her, just close enough for their arms to brush.

It was a fancy kind of ice cream; not the one her mom would usually buy her, or the kind the other kids were probably getting at the ice cream truck. It had a pretty wrapper and tasted like rainbow-sparkled strawberries, if there was such a thing.

A soft breeze rustled through the nearby trees and a bee landed on the rim of a plastic cup to inspect a drop of lemonade. Lexa glanced at the girl sitting next to her, carefully, so she wouldn't notice. She was pretty, Lexa thought. It made her chest feel fuzzy again.

A chuckle came from the girl next to her. "You have ice cream on your face."

"What?" And just like that Lexa's cheeks were on fire again. "Where?"

"Here," the girl laughed, poking at Lexa's chin.

Flustered, Lexa used the back of her hand to wipe it away. Still the girl looked at her curiously.

"What?" she asked, afraid there was more. "Is it gone?"

"Yes, it's gone," the girl laughed, as if she had just been messing around – but the sound of her laugh was nice, so Lexa didn't mind.

Somehow the girl managed to make her forget a lot of things, like the fact that her ice-cream was still melting and dripping onto her hand, and that you weren't supposed to disappear from your own birthday party, and… that she was supposed to take care of the bouncy house invasion.

A guilty feeling rushed through Lexa's stomach as she remembered. She had become so distracted that she had forgotten her friends were waiting for her.

She cleared her throat and cautiously jumped down from the bench, discarding her ice cream wrapper in a nearby trashcan. "I have to go do something."

The girl nodded and followed. "Okay. I'll come with you."

Lexa felt like she should protest, but the girl's hand crept back in hers – and for some unknown reason she didn't mind.

"Okay," she echoed.

Before Lexa would allow her friends to take over the bouncy castle (which she wasn't even sure she wanted anymore, because it might upset the girl currently holding her hand), she needed to make sure it was even there for her birthday to begin with. Maybe she had been wrong and it was really there for Clarke – whoever that was.

So she led them back towards the shade, where their moms were still talking about something probably not that interesting. (Her mother had a habit of talking about vegetables and supermarket prices – Lexa thought it incredibly boring, but other grown-ups seemed to appreciate it and she had no idea why.)

"Mom," she started hesitantly once they were close enough, interrupting the conversation, "did we order the castle?"

"We did," her mother smiled as they approached. Her brown hair was frizzy around her face and Lexa was glad she didn't look upset anymore. "Do you like it?"

Lexa nodded, her eyes sparkling.

"So… we can't play in it?" The other girl suddenly looked terribly worried. She sounded disappointed, and Lexa felt her stomach drop. Of course the girl could play in it, that isn't what she meant at all–

"Well, it is here for Lexa's birthday, Clarke," the girl's mother replied.

Clarke.

Lexa barely had a moment to register it.

"But I'm sure Lexa will share with you if you ask nicely."

Clarke turned to the girl beside her with a hopeful smile. "We'll share, right, Lexa?"

She nodded quietly, eagerly, feeling Clarke's warm palm pressed against hers. Of course they'll share.

No matter the strange, rowdy children that she didn't like or the bouncers who had tried to keep her out of her own castle or the glare Anya would probably give her once she found out that Lexa had made a pact with the enemy.

Because she and Clarke were friends now, right?

"We'll share," she confirmed, and Clarke squeezed her hand and grinned happily and Lexa was sure she'd made the best decision ever.

"Identify yourselves!" Anya's unmistakable voice shouted from the castle as Lexa and Clarke approached the drawbridge.

A water balloon splashed onto the ground in front of them.

"It's me," Lexa shouted back, unsettled, "don't shoot!"

"Oops." Luna's head appeared in one of the castle windows. "Sorry."

Armed with a couple buckets full of water balloons, Lexa's friends seemed to have moved into the castle while Clarke's party had gone out to the ice-cream cart. Now they apparently laid in wait, ready to defend it if needed.

"We're not taking over the bouncy castle," Lexa told them, giving a disturbed glance at the remnants of the thrown water balloon on the ground. "We're sharing."

"We're sharing?" Luna sounded doubtful.

"Yes," Lexa said. She climbed onto the drawbridge and waited for Clarke to do the same, making a point. "It's big enough for all of us, anyway."

Anya narrowed her eyes suspiciously. This seemed like a way too simple solution. She crossed her arms, leaning against the arched entrance of the castle. "What if they don't want to share?"

"It's okay," Clarke said. "They won't mind."

Before Anya had the chance to once more express her doubts, Clarke's friends returned with bright chatter and smudges of ice-cream still on their cheeks. Lexa tensed, expecting the worst. But still, no water balloons were thrown.

"Clarke," one of the boys called, unaware of anything and chewing on blue bubblegum, "you missed the ice-cream cart!"

"We were going to bring you a popsicle," Raven said, "but then we accidentally ate it. But it was melting, so we had to."

Clarke chuckled. "It's okay."

Lexa felt a hand wrap around her wrist. She fought the urge to entwine their hands again.

"This is Lexa," Clarke informed her friends casually. "The castle's actually for her birthday, but we're sharing."

Surprisingly, that was all it took. Clarke's friends cheerfully agreed and climbed into the castle again, fleetingly wishing Lexa a happy birthday as they passed her.

Inside, Anya was the first to meet the new group, wondering if sharing would really be that easy. The inflatable floor dipped as one of the newcomers came jumping towards her.

"Are you one of Lexa's friends?" The girl's eyes were big and her face painting of a butterfly was distracting.

"Yes," Anya said, trying to keep her balance on the wobbly floor.

The energetic girl grinned. "I am Octavia. And this is Raven."

She motioned towards her friend, who had the look Anya had expected all of them to have: skeptical, not entirely happy about having to share the castle. But this was Lexa's party and Clarke's party, and not theirs – so Anya bit her tongue and Raven said nothing either.

"I'm Lincoln." His smile was innocent and honest as he came up to them, like he couldn't feel the tension between the other two. Octavia couldn't either, apparently. Without another word she happily bounced away. Lincoln and the others followed, leaving Anya and Raven staring at each other with their arms crossed.

"I didn't know, okay?" Raven murmured, rolling her eyes. "That the castle was actually for Lexa's party, I mean."

It sounded strangely like an apology. Anya pursed her lips. "I voted to fight for the castle. But Lexa wanted to talk."

The corners of Raven's mouth twitched into a smile. "I would've fought for it, too."

At least they could agree on that, Anya thought. Raven moved back to the drawbridge, taking up the same spot as before.

"What are you doing?" Anya followed, watching as the other girl scanned their surroundings.

"I am guarding our castle," Raven answered as if it was obvious, "against intruders."

Anya tried not to smile. Their castle. That means she was already on the right side of the walls, and Raven didn't consider her an intruder.

"But you don't know who was invited to Lexa's party," Anya shrugged. "So I should probably help."

"Is this your birthday party too?" Lexa watched Clarke jump back and forth between the red and blue inflatable walls that caught her each time.

"Kind of." Clarke frowned, as if getting ready to tell a complicated story. "It rained on my birthday and mom had to work and then we went on vacation, so we're only having the party now. But I'm eight already."

Lexa thought about it, joining in on the jumping. Truth be told, she had never felt quite comfortable having a day that was all about her, when aunts and uncles pressed wet kisses to her cheek and squeezed her in for hugs and everyone wanted to talk to her to say their congratulations.

The presents were nice, of course. And the pancakes her mom made for breakfast.

But on her birthday there was always this odd feeling in the pit of her stomach, as there was now, every time she realized she would never be eight again, ever, for the rest of her life.

She sat down on the inflatable floor.

"Don't you think it's scary?" she said.

"What?"

Lexa shrugged. "Growing up."

Clarke stopped her jumping to plop down in front of Lexa.

"Well, maybe," she said, carefully inspecting the sudden change on Lexa's face. "But tomorrow you'll be nine, and everything else will be the same."

It was such an easy way of looking at it – as if they didn't have to worry about anything except today, and not tomorrow or next year or the rest of their lives. It made Lexa feel a bit lighter.

"I can't wait to be nine," Clarke informed her. "Actually, I can't wait to be twelve. And nine is closer to that than eight, so."

Twelve seemed like an eternity away. By then everything would be different, Lexa thought: she wouldn't be in the same school anymore and she wouldn't have to go to bed so early and she could get grounded if she wasn't home before curfew.

They sat cross-legged across from each other, lost in thought. The afternoon had almost passed. Their friends had gotten along surprisingly quickly and it was barely possible to tell the two groups apart anymore. They had spent a good hour jumping in the castle and making up games as they went, clumsy and giggling, until they were tired and thirsty and too warm.

Clarke and Lexa were the only two left in the castle now, their friends having made their way outside once Octavia suggested a water balloon fight.

"You're really nice, you know," Clarke said, chewing on her lip as a blush covered her cheeks. "Thanks for sharing the castle."

Lexa smiled, feeling the weird fluttery thing in her chest again. "Maybe next year we can have our party together."

By the grin on her face, Clarke seemed to think that was the best idea ever – until her eyes dimmed a little. "So we gotta wait a whole year again?"

Lexa shrugged. "Birthdays are only once a year."

"No, silly," Clarke rolled her eyes, "I mean until we get to play together again."

"Oh." That idea saddened Lexa as well. "I don't want to wait that long."

"Okay," the other girl said. "Then we don't wait that long."

"Good," Lexa breathed out, smiling.

They could hear their other friends laughing and shouting outside, and Lexa was suddenly really glad they had decided to share the castle. And strangely, she was also kind of glad that the builders at home weren't done yet and that the party had been at the park instead.

Yes, this was definitely one of her favorite birthdays so far.

Clarke smelled of sunscreen and vanilla ice-cream as she scooted closer.

"You know," she said, "I have the best birthday present for you."

"Really?"

Clarke nodded, looking at her with anticipation. "But you have to close your eyes."

Lexa did so, excited as to what kind of present her new friend could possibly have for her and then wondering if she should give Clarke something too, maybe–

Something warm and soft pressed against her lips and Lexa opened her eyes in surprise. She was still in a daze when Clarke pulled away from the kiss, giggling and watching the blush spread over Lexa's cheeks.

The summer-blonde girl stood up, keeping her balance on the wobbly floor of the bouncy castle, and started jumping around again, while Lexa just sat there with butterflies in her stomach.

"Happy birthday, Lexa."