A/N: Hey guys! This story was inspired by the comic series Super Sons which you should definitely check out if you haven't. It's basically Robin and Superboy going on missions together and messing it up because they are always at each other's throat. So I thought, why not make it with Supergirl and a female Robin? Who would cooperate? And why not make it Supercorp if I have the chance too? So this first chapter focuses on their first meeting, when they are around fourteen years old. The next chapter will show them a bit older, and then the last chapter they'll finally be dating.

Concerning canons, it's a bit of a mess, I must admit. The CW shows, the comics, maybe a tiny bit of the movies and even I'm not sure anymore? But, you know, it's endgame Supercorp, that's all that matters! I'll be posting a new chapter every day, so don't forget to follow if you don't want to miss a thing! I hope you enjoy!

Chapter 1
Robin and Supergirl

Lena was taken away from her homework by the sound of an alarm ringing from the bat computer. She smiled. Finally some action. She rushed to the computer and jumped into the seat. A Justice League alert. Even better.

Bruce came walking down the stairs quickly and raised an eyebrow when he saw her there.

"What are you still doing down here?"

"Working on my assignment," she replied simply.

"What do we have?"

"Justice League intervention in National City."

"Tell Alfred I shouldn't be long."

He turned around, about to get into costume, and Lena turned around in the chair and stood on her knees, to pout at him over the chair's backrest.

"Please, please, please, let me come with you! I'll just watch, I promise, I won't bother you."

Bruce shook his head.

"What about your assignment?"

Lena looked at the many mechanical components scattered on the workshop of the cave.

"I could really use a break. This one isn't even due until next month. I have time."

Bruce crossed his arm. He didn't usually bring her along for Justice League duty, because it was even more dangerous than usual Batman duty, but she was fourteen, almost fifteen now, she could probably handle it.

"Fine. But you'll stay put, away from the fight. Promise?"

"Yes, one hundred percent, yes!"

She jumped off the chair and ran toward the Batmobile, throwing her sweater off as she went. Of course, she was already dressed to go, her green and red robin outfit contrasting severely with everything around the cave. She went to fetch her cape, body armor, shoes and mask while Bruce went to get dressed as well.

When he was ready to go, Lena was already seated in the back of the Bat, mask on and belt fastened.

"Come on! We're going to miss everything."

"I doubt it."

He jumped in the piloting seat and they took off quickly. The Bat disappeared into the night and above the clouds, flying faster than any airplanes toward the West Coast.

"We've never been to National City before?" she questioned.

"No. Wayne Enterprise doesn't have an office there."

She huffed and crossed her arms.

"If we only visited places where you had a building we would be staying in Gotham all the time."

He chuckled.

On their way to National City, Batman confirmed a few things with other Justice League members, and Lena listened attentively. The threat was a small force of Daxamite invading the city. Three, maybe four ships, no more. Flash was already there, and Wonder Woman was almost there, just a hop away. Both Batman and Superman were on there way, and the DEO, with Martian Manhunter, was trying to evacuate as many citizens as possible. Lena was excited. An alien invasion with most of the Justice League on sight? There were reasons to be excited.

They had to lower their altitude when approaching National City, and Lena quickly saw the outline of the ships in the night sky. They were weirdly shaped, a bunch of triangles grouped together by their points to form a circular ship. The city was already on fire, but Lena noticed a red blur running around a few buildings on fire, and suffocating them quickly.

"Glad you could just us, Batsy!" Flash's voice came through the speaker.

"Where do you need me?"

"Center of town," Wonder Woman declared. "Superman will take care of the spaceships."

"Got it."

Batman flew the Bat around a few buildings, before finding one in construction, far from most of the chaos.

"Stay here. I'll come to pick you up when it's over."

"Got it."

Lena jumped off the plane and landed on the concrete floor with a roll. She stood up and turned around. Batman was still hovering there.

"And no fighting!" he shouted.

"I promise!"

He closed the cockpit and flew off. Lena came to stand as close to the edge as possible. The ships flying over the city all had green rays coming from under them. Lena first thought they were firing lasers, but the rays were continuous and didn't do any damage on the ground. They must have been some sort of teleporter.

Her earpiece suddenly came to life.

"Robin?"

"Yes, Batman?"

"Superman came with his cousin, she's going to stay with you while we deal with the chaos. She's new on Earth so be nice, okay?"

"When am I never nice?" she replied.

Soon enough, two blue blurs came to a stop in front of her. Superman, she recognized easily, she'd seen him a couple of times before. But the girl with him she'd never seen before. She had a blue suit and a red cape like him, as well as the S on her chest, but she looked almost nothing like him. Long blond hair flowing behind her, a bright smile on her face. She had his blue eyes though, that was the only thing they had in common.

"Robin."

"Superman."

"This is Supergirl. Can you watch over her while I take care of the rest."

"Of course, sir."

He looked at his cousin and nodded. The girl hovered toward the ground while he flew away. Lena watched as Supergirl came to stand beside her. The ethereal glow around her seemed to dissipate, maybe because she wasn't in proximity of her cousin anymore. All that was left was a shy looking teenager, all skin and bones in her slightly too big outfit.

"I am... Supergirl," she said with an accent only Lena's kin ear could pick up.

"Robin. It's a pleasure to meet you."

Lena held out her hand for Supergirl to shake. The blonde hesitated, her arm spasming a bit before she tentatively took Lena's hand in hers, very delicately. She pulled away very quickly, scanning Lena's face for any sign of pain, and let out a sigh of relief when there was none. Lena looked at her weirdly.

Supergirl moved away from her quickly and came to sit at the edge, to look at the city. After a moment of staring at the girl's red cape and flowing blond hair, she came to sit beside her.

"It is very pretty," Supergirl declared.

Lena looked at the city. It was like Gotham, maybe a bit brighter, or maybe that had something to do with the alien invasion.

"It reminds me of Argo City," she added sadly.

Lena frowned. There was no Argo City on Earth, she'd known that. It must have been on Krypton, after all, Batman had said she was new on Earth. She decided not to push it.

"Those stupid Daxamites always have to ruin everything!"

Lena frowned.

"You know them?"

"Yes. Daxamites are Kryptonian's cousins. I don't know how to explain. My English isn't very good, but I am working on it!" she added with a smile.

Lena found herself smiling back. There was something so purely bright and innocent about this girl, it was almost intoxicating.

"My cousin said you were Batman's sidekick?"

"I am," Lena added proudly.

"Then why are you dressed in red, when he is in black?"

Lena shrugged. She didn't really have an answer to that. Dick was the first robin, and his colors were red and green, so when she'd become Robin she'd kept the same colors.

"I don't know. I guess it's so he can't lose me in a fight."

This made Supergirl giggle.

"Where do you live?"

Lena hesitated. She wasn't supposed to talk about personal things, but then again Supergirl was a good person, a bit weird and surreal, but if she didn't reveal too much it should do.

"In Gotham, like Batman."

"I don't know where it is. I live in Midvale. It is very small. Not like here. I like here." she added with another bright smile, her eyes falling back on the city.
Lena continued to smile at her and looked back at the sky. Superman was currently pushing one of the ships back up in space, while everyone else was somewhere fighting down. She couldn't see them.

There was a sudden explosion not far, and Supergirl's smile quickly faded. Lena watched her with confusion. The blonde pressed her hands over her ears and screwed her eyes shut. She started groaning painfully as if she'd been hurt.

"Supergirl?" she called anxiously.

The blonde tried to scramble away from the edge, mumbling 'too much'. Lena jumped to her feet and pressed her earpiece.

"Batman? Something's wrong with Supergirl! I don't know what! Can you put me in communication with Superman?"

He didn't reply, simply passed her to Superman.

"Superman?"

"Robin? What's going on?"

"I don't know! Supergirl looks like she's in pain! She closed her eyes and her ears and I don't know what to do!"

"She's overwhelmed. Too much sounds, it's hurting her. You need to pull her somewhere away from the sounds and tell her to breathe."

Lena looked around. Supergirl was still wriggling on the ground, obviously in pain. The building was still in construction, but she imagined it would be fine if she could find a place less open. The elevator shaft.

She ran up to the elevator shaft and pushed the doors opened. The elevator itself hadn't been installed yet, but there were doors at every level, it should help. She threw a net grenade down, and it unfolded two levels down, creating a safety net for them to settle on.

Behind her, Supergirl had opened her eyes, and two angry red lasers had come out, piercing through the dark night and disappearing into the nothing. She closed her eyes once again. Lena didn't think, she picked up Supergirl under her arms and dragged her to the elevator.

"You need to breathe. Breathe. One, two. Come on, just breathe. Calm down!"

She realized she was panicking as well. She had a freaking out alien on her hands, one that could kill her in a snap, even by accident. She approached the elevator, and sighed:

"It's alright, I'm not throwing you to your death, there's a net," she warned, unsure whether Supergirl could even hear her.

She pushed the blonde down the elevator and watched her tumble in the net like a stone. The net bent under the weight but didn't break, to Lena's relief. She slid inside the elevator shaft and closed the elevator door behind her. She grappled onto the top of the elevator shaft and slid down until she could touch the net. There, she sat beside Supergirl.

The blonde was already a bit better, less forcefully trying to plug her ears shut. Lena found quickly that their common weight bent the net in the center, and they had no other choice but to sit side by side, glued to each other. Lena instinctively hugged the blonde and whispered to her:

"Breathe. One. Two. Slowly."

Supergirl's breathing relaxed after a while. She lowered her arms but kept her eyes closed a few more minutes.

When Supergirl finally reopened her eyes, she let out a long, painful breath. She tried to move away from Robin, but her hand passed through the net and she sent them both tumbling on their backs. Lena, surprised, didn't have the time to shift her weight and fell heavily, her arm pinned under Supergirl. Supergirl quickly flew off her.

"I am so sorry."

Lena stayed on her back, watching the blonde above her.

"It's okay. No harm done."

"No, I am sorry for earlier. It was the noise. I don't like loud noises too much."

Super senses, Lena remembered from what Batman had taught her on Kryptonians.

"Are feeling better?"

"Yes, thanks to you."

Supergirl looked around.

"Where are we?"

"The elevator shaft. It was the only enclosed space near us."

The blonde nodded.

"Should we go out?"

Lena nimbly stood up, her feet resting at the crossing between the ropes of the net. She picked up her grappling gun from her belt and was about to fire when Supergirl froze. Lena focused her hearing as well. She could faintly hear footsteps coming from the outside of the elevator door beside her. She whispered:

"People?"

Supergirl nodded.

"How many?"

Supergirl held out seven fingers.

"Hostiles?"

Another nod. Lena thought quickly. Some Daxamites must have seen Supergirl's laser vision. They would climb to the top and search for them. They could stay hidden here and hopefully not be found unless Daxamites also had X-ray visions. They had the advantaged right now.

"Can you fight?"

Supergirl grimaced. She assumed the girl couldn't really fight, just push things very hard.

"Distract them? I'll climb up."

Supergirl hesitated but nodded anyway. Lena grappled to the roof and jumped up, while Supergirl punched through the elevator door, sending them flying. Lena heard gunshots and loud bangs, and it made her heart beat frantically in her chest. She didn't know for how long Supergirl could hold, so she hurried.
She pushed the doors to the elevator open. The top floor was still clear. More gunshots echoed from under her feet. She ran to the edge of the rooftop and jumped.

Her cape deployed around her arms, and she slowly glided around the building. She turned her X-ray vision on with a quick press of the button on the side of her mask. She saw them, a level under her. Seven people fighting. One had already been knocked down by the elevator doors. Supergirl was in the middle of the fight, but she wouldn't hold long, Lena knew. She quickly devised a plan. They were probably stronger than her, but their bulky armor would hinder their movement. She could exploit that.

She aimed for one of the windows, and let her wings turn into her cape. She passed through the window feet first, her boots colliding with the helmet of the alien standing there. He fell to the ground, unconscious, and she rolled quickly. She picked up two tasing disks from her belt and threw them as she stood up. The Daxamite in front of her fell on his back, stunned. The four aliens left quickly turned around to look at her. They aimed at her but she rolled out of the way. She hid behind a pile of concrete bags and pulled her extendible staff from her belt. She could see two aliens approaching her from either side, while the two others were still trading punches with Supergirl.

She jumped on top of the pile of bags and leaped on the closest enemy. She trapped his head between her knees and used the momentum to pull him down, on his back. He fell heavily, incapable of stopping his fall, while she rolled off, landing in front of another alien. She extended her staff and hit him in the shin before standing up. He fell to his knees, and she swung the staff behind his helmet. He fell to the ground, unconscious. She turned around. The first one she'd pulled down was getting up. A swift kick in his under jaw knocked him out for good.

She heard gunshots, suddenly, and tried to jump out of the way. She felt something grazing her side and winced. Her skin burned painfully. She ducked behind the concrete bags once again and looked at her hand, pressed up against her side. No blood. She winced as she tried to look behind her. One of the aliens' lasers must have grazed her. She pulled her grappling gun, and, pushing past the pain, she stood up. The hook flew out of the gun and passed straight through the alien's shoulder, before pulling him toward her. He was knocked into the bags of concrete, and Lena, bringing both of her hands together and high above her head, hit him with all her strength on the back of his head.

She looked up. Supergirl was heaving, but intact, standing beside two unconscious Daxamites. She smiled when she saw Lena.

"Are you okay?"

"I am, don't worry."

"You fight really well. I don't know how to fight, really. My cousin said he would train me, but we don't have time. He is very busy with work."

Lena expelled the hook out of her grappling gun and placed the weapon back at her belt.

"Can you round them up? We'll tie them together so they don't run away when they wake up."

Supergirl nodded, and quickly ran around the empty level, at a speed too great for Lena to see her. When she was done, all seven of the Daxamites were seating, unconscious, in a circle, with the cable of her grappling hook tied around them.

"Is this good?" Supergirl asked.

"Perfect."

Now that they were tied up, Lena allowed herself a moment to breathe and wince painfully. The adrenaline of the moment had made her forget about the burning pain in her side, but now that she was seating again the bags of concrete, it came back to her in a head swarming rush. Supergirl frowned.

"Oh no! You are hurt!"

She rushed up to Lena's side, kneeling beside her to inspect her wound. Lena put her hand away. It was nothing really. The heat of the laser must have burned off some skin, but it was far less dramatic than it sounded.

"It's okay, really. I've had worst."

"May I help? I think I can."

Lena hesitated. She could just wait for this whole thing to be over, Batman would bring her back home and he or Alfred would know what to do. Supergirl insisted.

"Please? You saved us... To thank you?"

The proper words seemed to evade her, but Lena understood the meaning. Finally, she nodded. Supergirl took a step back and lightly blew toward her side. Chills erupted all over Lena's skin, raising the hair at the back of her neck. The air around her became terrifyingly cold, as a thin layer of frost formed over the burn. She sighed pleasantly. It did make her feel a lot better.

"Is it too much?" Supergirl asked worriedly.

"No, it's fine. Thank you."

Supergirl let out a relieved breath.

"I don't know how to control my powers well. Kal said not to use them too much, but you were in pain and I wanted to help and..."

"It's okay, really." Lena stopped the blonde's rambling.

She couldn't help but smile. This girl really was way too cute when she worried, she found herself thinking. She stared at her, amused by the blonde's antics. Supergirl started blushing and looked everywhere except at Lena.

"What do we do with them?" she finally asked, pointing to the bundle of Daxamites.

"I'll call Batman."

Lena pressed the earpiece and called out:

"Batman?"

"What is it?"

"We have a bunch of unconscious Daxamites on our hands. What do we do?"

"I told you to stay away from the fight!"

"Not if the fight came to us! Look, they saw Supergirl's laser vision, they came to us, we took them out."

"Leave them. Change building. Stay away from the fight. I'll come to pick you up when it's over."

He cut their conversation short, and Lena sighed.

"Alright. We have to change buildings."

She tried to push herself up and winced. The frost had almost completely dissipated, and it was hurting like hell once again.

"Here, let me."

"No it's..."

Before Lena could stop her, Supergirl leaned down and picked her up, as if she weighed nothing. She held her up against her, bridal style, and Lena felt ridiculous. She was being carried away by a girl smaller and more fragile looking than her. It made her look very weak, she knew.

"Hold on, okay?" Supergirl warned her.

Lena was about to protest, but Supergirl flew them through the window she'd broken when arriving, and she closed her eyes fearfully. There was a difference between flying on her own, where she could control what was going on, and being flown in another girl's arms.

"Which building?"

Lena forced her eyes open. Supergirl was hovering near their initial building, looking around. Lena saw that there was only one Daxamite spaceship left, which meant this entire mess was almost solved. She pointed to the building across the street.

"This one."

"Okay."

Supergirl brought them to the roof quickly, and she placed Lena delicately against the ventilation exit, so she could stay propped up and seated. Then, she sat beside her.

"Are you hurting?" she inquired quickly.

"No, I'm fine," Lena lied.

Supergirl nodded and relaxed a bit.

"I wish I could fight like you," Supergirl declared. "Did Batman teach you how to fight?"

"He did."

"Maybe he could train me too since Kal doesn't have the time."

Lena smiled.

"I don't think so. You're a bit too strong for us."

Supergirl pouted, just enough for Lena to think that the blonde reminded her of a puppy.

"That's what my sister says too."

"You have a sister?"

She nodded.

"Her name is Alex. She is my adoptive sister. Eliza and Jeremiah adopted me because Kal can't take care of me all the time."

Lena nodded.

"Batman adopted me too. I don't know how he found me but he took me in after my mother died."

Supergirl pursed her lips.

"I am sorry."

"It was a long time ago."

"My parents died a long time ago too, but it doesn't feel so long to me. It feels like it was yesterday."

Lena looked at Supergirl. There was something so deeply sad in her eyes, something she hadn't noticed before, behind all the happiness and optimism.

Superman was the Last son of Krypton, Batman had told her. Supergirl must have been its last daughter, then.

"I'm Lena, by the way," she introduced herself.

Supergirl's smile returned.

"Kara Zor-El."

When the Daxamite invasion was pushed back for good and the DEO had everything under control once again, Martian Manhunter thanked the Justice League for their intervention, and both Batman and Superman went to pick up their sidekicks. They found them still seating on the rooftop and talking about a show Alex had just shown to Kara, which Lena had never seen before. Superman thanked Robin for her help, and for protecting Supergirl. Lena smiled and replied it was nothing, and that if there was anything Supergirl needed, she could always call her. Once the Supers were gone, Batman was quick to call the Bat, and he helped Lena inside. She fell asleep on the way home.

A few days later, Lena was training in the Batcave when Alfred came to find her. She had already been punching the same sandbag for an hour, in sweatpants and sports bra, the bandage on her burn coming undone from her sweat.

"Mistress Lena?"

She ended her series of punches with a kick. The bag swayed on the chain, but she stopped it with her arm. She expected Alfred to reprimand her for training before her wound had healed. Instead, he declared:

"There is someone at the door looking for you. She said she was a friend."

Lena frowned. She didn't have friends. She'd graduated from high school a year ago, and she was following college courses from home because Bruce had agreed it would be a bit awkward for her to attend the classes physically. Maybe later. Maybe for her second Ph.D.

"Who is it?"

"She told me her name was Kara Danvers."

Lena smiled.

"Let her in, Alfred. I'll join her in a second."

"Should I prepare a snack, then?"

"Yes, please. That would be perfect."

He nodded and disappeared up the stairs. Lena picked up a towel nearby and hurriedly brushed it over her face and neck. She picked up her discarded tank top and put it on. She undid the straps around her fists and threw them on the nearby bench. She completely forgot to undo the ones around her feet and ran up the stairs.

She found Kara seating in the main living room, a bit flustered by everything precious-looking around her. Lena smiled. Kara was very different when she wasn't in costume. She looked even smaller, with a pale sweater a bit too big for her. She was wearing thick black rimmed glasses, exactly like her cousin's.

Lena walked into the room and sat down in the couch opposite Kara's.

"How did you find me?" she asked.

"Oh, hum... I asked Kal... I mean Clark. You said you would help me if there was anything."

Lena hadn't meant it literally, but then again she should have guessed the alien wasn't so used to what was literal or not on Earth.

"Sure, no problem. What do you need?"

Kara opened her backpack.

"I am sorry. I came here straight from school."

"You flew here? From Midvale?"

Kara nodded. She hoped Superman didn't know about this.

"What's so urgent?"

"I need help to train as a human."

"What?"

"Alex doesn't want to help me, she's too busy. But maybe you can help me. I need to learn how to be human. I don't want to push people in the hallway on accident and break their arms."

Lena ignored the fact that this was a very specific example and focused on Kara's problem instead.

"What do you need me to do?"

"You're human? Can you help me? I need to learn how to read the room, Alex said. Also, I don't understand Earth's social culture well."

Lena smiled.

"I will help you." she agreed.

Kara's smile could have illuminated the entire city at night.

"First, you really have to stop flying from Midvale to Gotham like that."