Disclaimer: I do not own Naruto or any associated characters.
Haruno Sakura was born into a civilian family. Her mom believed the whole shinobi thing was just a phase she'd grow out of. She thought that Sakura would eventually quit the academy, settle down with a nice young man, have a kid or two, and be the perfect housewife. However, that's not what Sakura wants.
When she enters the academy, Sakura is determined to get the best grades, and be the best she can possibly be. She never really considers training outside of school. Her mom always said that suitors wouldn't like muscular girls. It's not like she needs to train outside of class; she's already the top kunoichi. Sakura doesn't realize how paper thin that title really is.
Then, there is a boy, Uchiha Sasuke. Sasuke-kun is everything Sakura wants to be. He's strong, self assured, and cool; Sakura ends up developing a bit of a crush.
Upon graduation, Sakura is placed with Uzumaki Naruto and Uchiha Sasuke under the legendary Hatake Kakashi. She doesn't really read much into it. She's just excited to be on the same team as Sasuke-kun, nevermind the fact that she's paired up with the last Uchiha and the Jinchuuriki son of the late Yondaime Hokage (not that she knows the 2nd fact.) Sakura is someone administration thinks will never rise above chunin. She's a paper ninja who is more focused on her looks than training. She is no one.
On their first C ranked mission, Sakura is terrified. They face the Demon Brothers, and sure, she moves to defend the bridge builder, but what could she actually do against chunin level ninjas? She wants to back out. Naruto doesn't. Despite getting injured, he vows to protect the bridge builder. Sakura can't help being inspired.
Then they meet Momochi Zabuza.
Fear. Run. Hide. Fear. Run. Hide. She's terrified of him. She's completely and utterly terrified. She feels helpless. Eight points: Larynx, Spine, Lungs, Liver, Jugular, Subclavian artery, Kidneys, Heart. Run. Fear. Run. Fear.
Then Kakashi-Sensei is captured. Sasuke-kun and Naruto-Baka, manage to free him, Sensei defeats Zabuza, and everything seems to be okay again. Except it's not. She was useless. She was dead weight.
It turns out Zabuza wasn't dead. They learn tree walking, and Sakura reaches the top of the tree on the first try. Sensei may compliment her, but she doesn't like that he uses her accomplishment to motivate Naruto and Sasuke.
Zabuza attacks again, and she does nothing except stand in front of the bridge builder like a human shield. Naruto and Sasuke defeat Haku. Kakashi defeats Zabuza. Even Inari leads the villagers to the bridge in order to help them. Sakura, she does practically nothing.
Sensei enters them in the Chunin exams. Sakura doesn't think she's ready to be chunin. She's learned nothing but tree walking since becoming a genin. She enters anway. Sensei may say that it's their choice, but Konoha does everything in teams. The chunin exams will take place in teams; there is no question about it. Sakura enters. She doesn't want to let Naruto and Sasuke down.
The first phase is easy. Sakura is a paper ninja. She can do problems like these in her sleep.
The second phase of the exam is horrible. Fear. Fear. Fear. She can't move. She can't move. She's terrified. They're fighting against a sannin, and Sakura doesn't delude herself into thinking they can win. They're hopelessly outmatched. Sasuke is bitten, and Naruto is knocked out. How can she possibly protect her team? She's dead weight.
Sakura manages to bring Naruto, and Sasuke to safety, but she can't keep them safe. She's exhausted, and when the team from Oto attacks, she loses badly, but she doesn't give in. She keeps fighting. She may only be a kunoichi in name, but she's not going to let anyone harm her team. She cuts her hair to escape, and damn does it feel good. She's not going to just play kunoichi anymore, she's going to train her butt off and be one. She doesn't advance to the third phase, but that's okay.
Somehow, the third phase ends up being even worse than the second. Suna and Oto attack. Her village is invaded, and she is no help. Sasuke may not defeat Gaara, but at least he stands a chance against him. She doesn't. Naruto of all people manages to stop Gaara.
The Hokage is dead.
The village is (somewhat) destroyed.
Team 7 is fractured. Sasuke abandons the village. Naruto leaves to train with Jiraiya. Kakahsi disappears to who knows where.
Sakura is a no name ninja. She is the one civilian born of a graduating class of clan heirs. Sakura doesn't plan on staying a no name ninja. First, she'll make chunin, and then she'll make jounin.
She finds Mitarashi Anko, the proctor of the second exam, and demands to be her apprentice. The woman throws dango sticks at her. Sakura comes back the next day, then the next, and the next.
After a few days, Anko takes Sakura by the arm and shunshins them to a nearby training field. "Since you won't stop bothering me, you must be quite serious about this. Let me ask you this brat, why do you want to be my apprentice?"
"Team 7 is… gone." Sakura mutters, staring down at her hands. "I wasn't good enough. I want to be able to stand on my own. You work in T&I. You know exactly how far you can push someone until they break. I need someone who can push me to my breaking point each and every day."
"Why not ask Lady Tsunade to be your mentor? I've heard you're intelligent and have impeccable chakra control; you'd make a great medic. Your team could be the next generation of the sannin."
"I don't want to be a medic." Sakura snaps. "I don't want to stand on the sidelines. I want to fight."
"Hmm, alright brat. I'll teach you. But I won't just teach you how to fight. I'll teach you to use every dirty trick to win: Posion, stealth, seduction, mind games, even torture. If you're going to be my apprentice, you're going to be the best damn apprentice possible."
"Thank you! Thank you! Thank you!" Sakura grins.
"Don't thank me brat, you'll be cursing me by the end of the day."
"What do you mean by that…" Sakura yelps, ducking as several kunai fly just over her head.
"Lesson one, dodging. I hope you learn quickly; all my kunai are poisoned!"