10 Chapters! And my first A/N for this story! Warning: This is extremely long, and possibly convoluted. Sorry. I just wanted to explain some things about this story. First off, this is mostly canon-compliant. It only diverges in a couple of areas. So, there's a couple of things I'd like to address.

1. Percabeth: While I have nothing against this ship, I couldn't have Percy date Annabeth because I felt like she would limit his ability to interact with Natasha without revealing their sibling relationship with everyone. Also, Percy would go to university in New Rome with Annabeth, leaving no room for becoming the Sea Scorpion. I might have Percy ask Annabeth out waaaaay later, but it's going to be a long time before that happens (if it does).

2. Timelines: I had to mix around the timelines a bit so that I had a smaller age gap between Percy and Natasha. Now, she's only 12 years older (Pietro Maximoff: You know, I'm 12 minutes older than you) than Percy. Also, there are some other changes, like the amount of time between the Avengers and CA:TWS (More on that below).

3. Behind the Scenes: A lot of what I have so far would be behind the scenes in the actual books/movies. Some of it does change small details about what happens at certain points. But then again, this is fanfiction, so I do have some liberty here.

4. Future decisions: In the future, I'm probably going to have to bring in other parties, namely the Guardians of the Galaxy, the X-Men, and the Agents of S.H.I.E.L.D. because in order to take this story as far as I'm going, they'll have to pop up. Probably not going to include the demigods of CHB/CJ, the Egyptians, or the Magnus Chase Norse Pantheon, because Percy probably wouldn't want to put that on their shoulders if he can avoid it. Also, mythological reveals would probably create unneccessary chaos right before the finale, and that's not helpful. There will be references and mentions, as well as guest appearances, so no worries about that. But going back to my original point, I'm going to have to twist some events to insert some characters, and perhaps mess with realities (Because X-Men: Apocalypse and Wanda's Comic Book Powers) for the sake of continuity. However, no matter how many characters I add in, this fic will mostly focus on Percy and Natasha's sibling relationship with a side helping of canonical pairings. And pairings won't change, sorry. As they stand: Bruce/Natasha; Clint/Laura; Tony/Pepper; Thor/Jane; Steve/Sharon. Oh, and Solangelo, Frazel, Jasper, and Caleo will have appearances as well!

5. The way this story is set up: It's laid out so that every 5 chapters is a story arc. The first 5 was the backstory of Percy and Natasha's sibling relationship + it covered the PJO books, Iron Man 2, and the first Avengers movie. Chapters 6-10 are focused on the time between the Avengers and Captain America: The Winter Soldier. Canonically, that was like two years, but I've shortened it to a couple of months, because I don't want Percy to age too fast in this story. You might notice that the first five chapters have Percy in the title and the last five chapters (including this one) have Natasha in the title. The title will give you a hint as to who the chapters are more focused in on. Natasha and Percy will always have at least one P.O.V. between the two of them per chapter, but if a different character's name is in the chapter title, you'll be getting a P.O.V. from them as well.

I've got the next 20 chapters sort of planned, and that doesn't even cover CA:CW! Twists and turns should be expected in my non-canonical version of that movie. Just so you know, my chapters tend to be anywhere between 2,000 - 3,000 words long. They might get longer, but we'll see.

By the way: May_West and 123yyy123123, thank you guys for reviewing my story! thatgirlCV and Honeyfern1026, thanks for voting on it. I hope you all continue to enjoy it! If you guys have any ideas, feel free to let me know! For any other readers, please review! They really make my day, and help me write faster!

Disclaimer: I don't own the Avengers or PJO/HOO.

Alright, on with the story!
-Spathi

Natasha's P.O.V.

She woke to the sound of her phone chiming with a text alert. She groaned and grabbed it, blearily taking in her surroundings. The time read 7:00 AM. The last thing she remembered was sitting at the communal kitchen table, shaken by a nightmare. "But if that's the case, how did I end up here? Maybe that was part of the dream." she thought as she turned her gaze to her phone.

Relocation Alert: Washington D.C.

Departure: 2300 hours, today

Team: Steven Grant Rogers a.k.a. Captain America; Natasha Alianovna Romanoff a.k.a. Black Widow

Notes: Report to Director Fury's office at the Triskelion at 0900 hours tomorrow (EDT)

Natasha sat up, and reread the alert. Then, she changed into a hoodie, tank top, and a pair of sweatpants. "I'm being reassigned to Washington D.C.? Straight to S.H.I.E.L.D. HQ?" She mind-messaged Percy, telling him of her reassignment. Moments later, Percy knocked on her door.

"You can come in." she said out loud. Percy did, looking at her questioningly. She tossed him her phone, and he read the alert. He raised an eyebrow at her.

"Triskelion? That literally means three legged." he commented.

"Looks like I'll have to pack." she replied.

"Well, we should probably make a stop at the Bunkers to get you some weapons. But first, you should tell Bruce." Natasha nodded in acquiescence.

"Hey, Jarvis?" she asked.

"Yes, Miss Romanoff?" the AI replied.

"Where is Bruce?" she questioned.

"He is currently in the gym, stretching. Shall I inform him that you are looking for him, Miss Romanoff?" Jarvis responded.

"No, we'll just head down to the gym. Thanks, Jarvis." Natasha said.

"Certainly, Miss Romanoff. By the way, Mr. Rogers has entered the building." Percy held a hand out to his sister, and she took it. They dissolved into mist and reformed in the middle of the gym, where Bruce was sitting in full splits. Natasha raised an eyebrow.

"Are you sure yoga isn't part of your secret to staying calm?" she asked. Bruce chuckled

"Actually, I do practice yoga. And I freerun, in my spare time." Percy looked confused. Natasha laughed.

"I'm aware that you can do parkour. I also know that you can disappear really easily. I've seen the videos of you on the run from General Ross." Bruce nodded his head in understanding.

"Hey, I've got an idea. Grab Tony and Steve, and go out to Central Park. Play a game of disguises. You've got to enjoy your last day here, Tash. I'll just swing by later in the day to see you beating them by miles. I need to run some errands for mom first. Then I'm going to lunch with some of my friends. So just have some fun!" Percy suggested. Natasha shrugged and Bruce frowned.

"Last day?" he questioned.

"I'm being relocated to D.C. with Rogers for some time." Natasha explained. Bruce smirked.

"In that case, we totally have to screw with Tony and Steve by disappearing on them, and popping right back up." he said, rolling backwards and springing up to his feet. Natasha grinned.

"I like the way you think." she replied, heading for the door.

Hours later, Tony, Steve, Natasha, and Bruce stood in the middle of Central Park, wearing civillian clothing.

"Wait, so what are we doing?" Tony asked. Natasha smiled.

"Well, let's make a bet." Tony suddenly looked interested, and Steve looked wary.

"I'm listening." the billionaire replied, leaning forwards.

"We're splitting into teams. You and Steve against Bruce and I. First off, you and Steve are going to chase us through the park. If you can't catch us in the next two hours, you lose that round. If you do, you win the round. Catching entails grabbing hold of one member of our team for three seconds. Next, Bruce and I will attempt to disguise ourselves in Central Park Conservatory Garden. We won't leave the garden. All you have to do is find us. You'll have two hours to find us at least once. If you win both rounds, then you get to make us do something for you, but it can't be something ridiculous. If you win a round, and we win a round, then we'll think of a tiebreaker. And if we win both rounds, then we'll get something from you guys. Deal?" Natasha explained. Tony turned to Steve questioningly.

"Alright. It sounds fun." Steve said. Natasha grinned and exchanged a look with Bruce.

"Okay. Time starts... now." she said, dashing off. Bruce ran off in a different direction.

"I'll chase Bruce, and you chase Natasha." Natasha heard Tony yell. She heard Steve gaining on her, and sprinted at a lamp post. Once she got near enough, she jumped up, and swung around the lamp, flying over Steve's head. Steve had way too much momentum, and couldn't slow down quickly enough, so he ran past the lamp, giving her a head start. She bolted back the way she came, catching sight of Bruce running from Tony, easily dodging past joggers, children, and other civillians. Behind her, Steve was catching up. She spotted a tree with branches about 10 feet off the ground.

"Hey, Bruce! I'm going to need a boost!" she yelled, and he looked over at her, not breaking stride. She motioned at the tree, and he nodded, bending over a bit as he ran. She leaped onto his back, and he straightened, launching her up into the branches of the tree. She glanced back to see Bruce do a butterfly twist over a bench; that is, he launched himself over it, twisting through the air parallel to the ground before landing.

"What the hell?" she heard Tony cry, and she laughed, before focusing back on the super soldier chasing her. She noticed a high wall near her tree, and she smiled. "Perfect.", she thought. She ran down the branch nearest the wall and flipped off it, landing neatly on the top of the wall. She hopped off, and started moving again. Steve was starting to get closer to her again, so she ran towards the basketball courts, which were surrounded by a high fence. She kicked off a nearby tree, landed halfway up the wire fence, and started climbing. She ran on the top of the fence with perfect balance, causing several teens playing basketball to stop and gawk at her. She leapt off the other side, rolling when she hit the ground. Steve was forced to find a way around the fence, and she took the opportunity to head for an area with more trees. Bruce called to her from the top of a tree. Tony was circling the trunk below him.

"Over here!" the doctor yelled. She ran towards his tree, dodging Tony, and Bruce swung down, allowing her to grab onto his legs, and let him swing her up to his branch. The duo looked down at the other team, who was breathing hard.

"Giving up already?" Natasha asked innocently.

"Steve, you chase Bruce. You have a better chance at catching him than Natasha." Steve nodded, and Bruce frowned.

"I-" The scientist jumped down, dropped low, and whipped his leg in a circle, neatly sweeping Tony and Steve off their feet.

"-take offense to that!" he continued, taking off running. Natasha laughed, watching Steve groan, get to his feet and run off after him. Tony lay on the ground, the breath knocked out of him. Natasha looked down at him, a smug smirk on her face.

"You haven't won yet, Romanoff." he wheezed. Natasha grabbed a hanging acorn and dropped it on his chest. It landed with a satisfying thunk.

"That was cruel." He started to get up, and Natasha chose that moment to hop down, knocking Tony back to the ground again. He swore, and Natasha smirked at him before dashing off. She ran up the side of a wall of a cement structure, and sat on top, watching Tony fruitlessly make his way towards her. From her vantage point, she could see Bruce giving Steve a hard time by running directly into a large group of people and easily dodging past every single one of them. Steve, who was not as adept at juking, slowly and politely made his way through the crowd. Tony looked over at Steve and face palmed, causing Natasha to internally burst out laughing.

By the time two hours had passed, the two men had not caught Natasha and Bruce. They had tried their best, both chasing after one of them, then the other, trying to corner both of them, attempting to circle around, but Natasha and Bruce had managed to foil each and every one of their plans.

"Fine, you win the first round. But it's not over yet!" Tony said, breathing hard.

"But first, we should get lunch. It's around noon, and I'm sure we are all hungry after all of that running." Steve said. Everybody agreed, so Natasha found herself sitting on a bench with three other Avengers, eating a hot dog. Natasha thought it was a miracle that nobody had recognized them, seeing as two thirds of the Avengers were all in one place. Then, she spotted Percy walking past with a group of teens she recognized as the Seven, as well as Nico. There was also a black haired girl with electric blue eyes she hadn't seen before.

"Tell your friends to maintain your cover." she mentally told Percy, who stiffened slightly before nodding his head a tiny bit. She watched his features change slightly, due to the mist. He whispered something to his friends, probably explaining the situation before walking over.

"Oh my gods. Mini Stark is here. And Stark is at the end of this bench. Oh no." she realized. She passed the thought on to Percy, whose eyes widened. He passed it off as excitement as he spoke to the assembled Avengers.

"I know you!" he said to Tony. He glanced at the other Avengers.

"I know all of you! You're Avengers. I'm Pericles Johansson, but most people call me Perry. These are my friends." he continued excitedly in a low voice. Each of the teens introduced themselves. The girl she hadn't seen before, whose name was apparently Thalia, narrowed her eyes at Bruce.

"Hey, didn't we see you at that coffee shop in Cloudcroft, New Mexico? Like, five years ago or so. You were working at the register. You looked really tired and lonely. That's why I remember you." she asked. Bruce frowned, trying to remember.

"Now that I think about it, yeah. There were five of you. That was shortly after my accident. I know that you and Perry over here were there. There was also the curly haired kid, the girl with coppery skin and dark brown hair, and the other younger girl with black hair and olive skin. That girl looked a lot like you, actually." The last part of his description was directed at Nico, who looked slightly uncomfortable.

"She was my sister. She and the girl with coppery skin died in an accident days later." he said. All of the teens looked solemn. Percy had an almost guilty expression on his face, and his fists were clenched. Natasha decided to change the subject.

"So, is there any particular reason why you came over here? Did you just want to say hi?" she questioned. Leo, the mini Stark, lit up.

"Oh, yeah. Mr. Stark, could I get your autograph?? I'm a huge fan!" he said, and then proceeded to start talking about some machines he was inventing. What Leo was saying didn't seem to make sense to anybody but Tony and Bruce, who both looked impressed. Tony gave Leo the autograph, and turned to Piper.

"Isn't your dad Tristan McLean? He's been to a couple of my parties. I've seen you before, talking with Rachel Dare." Piper nodded, and Tony smiled. Eventually, each teen had all four of their autographs. Bruce spoke up.

"So, do you guys have any siblings?" he asked curiously. Thalia smirked.

"Jason here is my brother." she replied, ruffling Jason's hair. Nico gestured to Hazel.

"Hazel's my sister." he said. Piper, Leo, Frank, and Annabeth mentioned that they all had a number of half-siblings. Tony turned to Percy.

"I've got a sister who's 12 years older than me. Her name's Scarlett." Percy said with a tiny smile.

"Scarlett?" Natasha mind-messaged Percy.

"You have red hair, okay? And it's a pretty normal name!" he defended himself.

"Alright. Just asking." she thought back.

The teens and the four Avengers chatted for a little while longer before Percy looked at his watch.

"Guys, we have to go! You're due back at camp in 30 minutes." All of the teens looked slightly panicked.

"It was nice talking with you all, bye!" Percy said quickly, and they all took off running. The four Avengers shrugged.

"Let's head over to Central Park Conservatory Garden. We have a game to play." Bruce said. They walked over. Tony and Steve entered in front of the other two.

"Alright." Tony started, and Natasha glanced at Bruce, who smirked. They slipped behind a bush. Natasha shed her hoodie, and tied it around her waist, while Bruce took off his long sleeve plaid button up, revealing a white wife beater. Natasha peeked through the bush to watch Tony and Steve's reaction to their disappearance.

"When do we begin?" Tony finished, spinning around to face Natasha and Bruce. Steve turned as well, and Natasha kind of wished she had a camera so that she could take a picture of the duo's comically bewildered expressions. She remembered her phone, and snapped a photo. She looked at Bruce to see that he had donned a baseball cap and was wearing it backwards, effectively hiding his curly hair. He also had a pair of sunglasses. She noticed that he actually had quite a bit of muscle, which was usually hidden by his loose, long-sleeved shirts.

Natasha put her hair up in a messy bun, popped some brown contacts in, put on a pair of sunglasses, used makeup to alter her features slightly, and slipped an Avengers themed T-shirt that she had bought discreetly over her tank top. Then, she stepped out from the bushes, Bruce following her. Tony and Steve walked by, and she turned to Bruce, who to her endless amusement, had pulled a cigarette out of nowhere and placed it in between her teeth. She caught his eye, and he slung an arm around her, and she leaned into his side, giggling. Tony and Steve barely glanced at them. Bruce kept his arm around her, and they kept walking, enjoying the sunshine.

A little while later, while they were wandering the maze on one side of the garden, Natasha noticed Steve and Tony approaching them again. Bruce suddenly started a conversation with her.

"Hey, babe. I'm thinking that we could go for a ride out of the city on my motorcycle later, maybe have a little picnic in the forest, enjoy nature. What do you think?" he said in a gruff, deeper pitched tone with a Southern twang.

"You do have a soft side! I never would've guessed that you were such a romantic." she replied in a higher pitched voice with a slight Texan accent.

"Hmph. Only for you. Don't go around soiling my reputation." Bruce grunted. Steve and Tony passed, and Natasha quirked an eyebrow.

"Texan biker?" Bruce shrugged unapologetically.

"It was the first thing that came to mind." he defended himself.

"It was good. Color me impressed." she said.

Near the end of the two hours, Natasha was sitting on a bench with Bruce when she heard Tony's voice.

"These glasses have JARVIS built into them. We can run facial recognition. Romanoff never said anything against it." Natasha cursed mentally.

"Wait, you've been carrying those around this entire time?" came Steve's disbelieving voice.

"Maybe." Tony replied. He entered her line of sight wearing a pair of hi-tech glasses. Natasha's mind whirled, trying to figure out how to move from their location without Tony running the facial recognition on them. Tony and Steve came closer and closer. Then, Bruce did the unexpected. He pulled her onto his lap, cupped her face with his hands, and kissed her.

Natasha's mind went blank for about half a second before she realized she needed to react. She wrapped her hands around Bruce's neck, and closed her eyes, doing her best to continue the act while also listening for the other two Avengers. "Bruce is good at kissing." she mentally noted.

"Can't get a read on those two over there on the bench. I can't see enough of their faces." she heard Tony say.

"The ones that are kissing?" came the reply from Steve.

"Yeah, okay. It's not like those two would be Banner and Romanoff. That guy looks like he works out often, the girl is wearing an Avengers shirt, and they are making out. Seriously, how would it be them? There is no way Bruce would have Natasha on his lap and be smooching her just to disguise themselves." Tony responded.

"Tony, you're staring. It's weird. Let's move on." Their footsteps faded away, and Bruce pulled back, breathless.

"Sorry." he said immediately.

"No, it's fine. It was a brilliant idea." she assured him, smiling.

"I thought you said you didn't like him." Percy mentally said, and she internally swore.

"You're here?" she asked.

"At your 6. Nice show you put on. You seemed really into it."

"We are done talking, creep. Go away. Just get the tech I'll need for D.C."

"Ok. I'll send you the picture I took."

"What!?"

There was no reply. Bruce looked concerned.

"Are you okay? You spaced out for a bit." he said.

"I'm fine. It's been two hours. We should probably undisguise." she suggested. They moved behind a bush. Bruce put his long-sleeved shirt back on, and took off the hat and sunglasses, tucking them into the waistband of his pants and his pocket respectively. Natasha wiped off the makeup, let her hair down, pulled off the Avengers shirt, shed the sunglasses, and put everything back into her small bag, which she immediately concealed.

"So that's where you had everything." Bruce mused. She put a finger over her lips. They made their way over to Tony and Steve.

"Where even were you??" Tony exclaimed. Natasha smirked.

"That's for us to know, and for you to wonder at eternally." she said. Tony grumbled, Steve smiled, and Bruce laughed. They headed back to the tower, and Natasha went to her room to pack for her relocation. She decided to leave most of her clothes there, as she could just buy new clothes. She put all of her weapons, concealed as normal objects, into the duffel bag. Someone knocked on her door.

"Come in!" she called, and Percy walked in holding a box.

"I've got a photostatic veil, a couple of stun disks, a voice modulator, and a present for you." he announced, dropping the box on her bed.

"A present?" she asked.

"Yeah, I got Leo to help me with it. They're new and improved electroshock bracelets. Each capable of shooting a grappling hook, emitting a really powerful jolt of electricity which can be adjusted to stun or kill, as well as storing ammo and small items, such as your stun disks, veil, and voice modulator." Natasha took the bracelets with a thankful smile. She put them on and inspected them. They were silvery black, similar looking to the ones she had before, but they were sleeker and lighter. She figured that she could hide them under her sleeves in public.

"Oh, and one more thing. Grab the end nearest you, and pull it towards the tip of your hand. For both bracelets." She did so, and her hands were suddenly covered in black gloves made of interlocking Stygian Iron and Vibranium plates, which fit closely to her hand.

"They're shock absorbing, like mine. Try firing both of your bracelets at the same time while holding them near each other." Percy continued. Natasha aimed her fists away, and tried it. Her gauntlets created a force field in the shape of a shield in front of her. The force field crackled with red electricity. She noticed that instead of the normal blue, her bracelets' wiring glowed a deep red. She had a strange idea, and bent her arms a little. Percy's eyes widened.

"Wait-" Natasha straightened her arms, pushing outwards, and opening her fists. The force field swelled, and a wave of pure energy expanded forwards. This had the added effect of leaving a gigantic space where the wall was. She could now see her living room, which was covered in debris. She turned to Percy, who looked rather shellshocked.

"Um. According to Leo, the close proximity of the bracelets creates some type of electromagnetic field and causes the energy wave. If the bracelets are set on their highest voltage, and you push as hard as you can, you'll be able to do a lot of damage. Not sure how much, but definitely a lot." he said. Natasha blinked, deactivating them.

"Good to know." she responded.

"Those are a last minute resort, okay? I really hope you don't use them." Percy said seriously.

"I'll be fine, Percy. Don't worry." she assured. Percy smiled slightly.

"Okay, Tash. I trust you." he replied. He gave her a hug, and disappeared. The elevator doors started to open, and Tony, Steve, and Bruce walked out. They stopped in their tracks and stared.

"I accidentally created an expanding electromagnetic field with my bracelets, shock disks, and a very high voltage." she said. The three men continued staring. She sighed, and hefted her duffel bag. She strode past them into the elevator.

"Come on, boys. I've got a plane to catch." she said with a smirk on her face. The elevator doors closed behind her, leaving three dumbfounded men on her floor.

"What the hell?" Tony whispered, assessing the damage again. He turned to Bruce and Steve, who shrugged.

"That woman is terrifying." the billionaire said. The other two men nodded in agreement. None of them noticed a small robotic spider sitting by the elevetor, mechanical eyes fixed on them.

 Thirteen floors below them, Natasha smiled, having seen the entire conversation through Zvezda's eyes. 

Hope you enjoyed! Please review!