If you don't know what Naruto is (or at least have heard of it), you most likely have been living under a rock for the last 3 years. But don't worry, here's a brief introduction. Also, spoilers ahead.

The first long-running manga created by Kishimoto Masashi, Naruto began its serialization on November 1999 in the Japanese magazine Weekly Shounen JUMP, published by Shueisha. With more than 36 volumes out, the series is still on-going. In 2002, Studio Pierrot made an animated adaptation of the manga, which run for 220 episodes and covered the so-called part 1 of the story. Shortly after, a continuation named Naruto: Shippuden began airing in Japan.

Naruto tells the story of one 12-years-old ninja apprentice called Uzumaki Naruto and his coming of age in a world which is entirely too dangerous for kids his age. Cursed to remain alone for most of his childhood due to a demon fox which was sealed inside of him (in order to save the village he lives in, I should add), Naruto is assigned to Team 7 to continue with his ninja learning. And that's when he really gets in contact with the first two people he would consider friends, and the ones with whom he'll form an indestructible bond: Uchiha Sasuke and Haruno Sakura.

Uchiha Sasuke is what every kid his age (or at least Naruto) aspires to be. Top of his class, good-looking and popular among the girls. What no one knows is that inside Sasuke's cool and mysterious exterior, there's a lonely child whose older brother slaughtered his entire clan. Being the only one left alive by his brother, the boy is filled with guilt and thirst for vengeance towards the source of his suffering.

Such is this drive, Sasuke sees nothing but the path he must follow in order to kill his brother, no matter the personal cost, no matter the unhappiness it brings him. However, when he is assigned to Team 7 and slowly begins relying and trusting in both Naruto and Sakura, he sees his determination wavering. For the first time he's found people that are important to him and for whom he'd do anything... he feels happy again for the first time ever since he lost his family.

Concluding that his goal will forever be unreachable if he keeps softening due to his team mates, he decides to sever all the bonds that took him so much effort to build and leave home in order to obtain power without such distractions.

Haruno Sakura would seem like your average teenager girl. And she is, to a certain extent. Her childhood is not shadowed by a terrible tragedy, but only minor issues. She's got parents and had at least one friend, so she's not familiar with feelings of extreme loneliness. She's got a crush on the most popular guy in his class, while she's also quite the brain among her class mates.

Her assigment to Team 7 affects Sakura deeply and in ways she would have never imagined. She not only learns what team work is, but she also is taught to not judge people by their cover, and how it is to care about people more than she's ever done in her life. As she gets more and more attached to Naruto and Sasuke, she starts wanting to become stronger -- both inspired by them and also due to her desire to protect them from whatever threatens their happiness.

Sakura becomes a determined and incredibly strong person, something that hasn't got anything to do with physical training, but with her will to excel and devote herself to the important bonds she's been able to build at last.

You could say Sasuke & Sakura had a bumpy start. She had a crush on him that had nothing to do with who Sasuke really was, and he was annoyed at Sakura's superficial ways of judging people (both him and Naruto, even if differently). Despite this, Sasuke had his heart in the right place all along, for Sakura (and their client) was the first person he shielded an attack for.

Some people forget about this, but Sasuke is actually the one who has always taken the first step. He was annoyed at Sakura's comments on Naruto's childhood, he somewhat confessed to Sakura about his feelings on his past and his brother (a long time before all of us found out), he offered Naruto food when Kakashi told him not to, he shielded Sakura from danger and took a deadly attack trying to protect Naruto. By the end of their first important mission, both Naruto and Sakura had shed tears for Sasuke. There was no way back from then on.

The chuunin examination meant lots of changes for the pair. They shared painful experiences by themselves which eventually led to Sasuke getting his cursed seal from Orochimaru. Sakura witnessed a fragile side to Sasuke she had never seen, she saw him in weakness and also transforming into a person she knew wasn't Sasuke -- till she stopped him. After these events, Sasuke begins to rely on her and even going as far as to single her out in several occasions ("not even you").

Indifference becomes friendship becomes profound familiarity. Despite Sasuke being quite the closed book, the fact that one of the things that triggered his flight from Konoha Gakure was his inability to protect Sakura (while Naruto could), says lots of things about him.

And in Sakura's case, her discoveries about the real Sasuke only causes her to fall in love with him for real this time, her devotion showing in every way possible. Going as far as offering help to avenge his clan, whenever he'd go, whichever side he chose to take.