It started when they were on their way back home from Land of Waves mission. No, it actually started when they witnessed Zabuza's death.
Woke up from a nearly death experience, Sasuke noticed 3 things.
One, he had decisively admit to himself, he values Sakura more than anyone alive. It's not the first time he woke up from pain and unconsciousness. But its the first time he woke up to someone crying over him, fretting over him, worry about him like she did that day. He knew from that moment, Sakura was a precious person. He knew it back then, as a comrade, but now, she is a precious person to him as herself.
Two, he wanted to protect her at all cost. He needed to protect the fragile annoying girl that unknowingly became so important to him. He doesn't want the thing as the like of the massacre to happen ever again.
Three, he's mortal. In fact, that's the most he's noticed of all three. And that worries him. What happen if he died? If he's not around to save her. Who will be there to protect her? The usuratonkachi will always make things worst as it already is. He can however trust him on it. But he couldn't fully rely only on him. Kakashi isn't there all the time either. She needs to learn to protect herself, he thought.
That's how the thought of finding something in Sakura which worth train for. He knew first hand that Sakura is the best at analytical skill, however it ended just there with maybe her genjutsu resistance. But that's it.
He turns his gaze to Sakura, who walks surprisingly silent beside him. Kakashi and Naruto walking just a few feet before them, with the later talking loudly as he usually did.
Back to the pink haired girl beside him, he study her. She's so small, no any sign of muscle. From their training sessions, he learnt that she's very weak in taijutsu and only knew basic ninjutsu. He couldn't blame her on that though, she came from a civilian family, anyways.
With his preception on her, he look at her face who is focusing on the surrounding beside her, the look of innocent expressive bared her face, eyes shone with adore as she looks around them. They are currently walking beside a cliff; she's looking at a large and rather tall tree situated afar from their location.
Tree. He thought. And then his mind flash back to when they learnt to walk on tree during their stay at Tazuna's house. Sakura's chakra control is almost perfect. He realized.
There must be something to use with that skill. His thoughts lingers on that for quite sometime. He remembers how hard he and Naruto trained to achieved what she already did on first try. That's when he got it.
He applied too much chakra on his feet, which has him not only unable to walk too far up but also caused the dent on the tree, as if he had kick it there, hard. If Sakura can control her chakra to certain place precisely, she might use that to an advantage. She doesn't really have to be strong to do that.
"Sasuke-kun." He heard her soft melodic voice call for him, questioningly. His gaze is still on hers as she stares at him, looking shy with that blush on her cheeks.
Sasuke turn his face to their blonde teammate and teacher, "I was just thinking." He responded after a few moment, than look back at her.
"What is it?" She asks, interested. Sasuke is never one to start a conversation, especially with her. So when he did, of course it will attract her giddiness, regardless of whats it about. They stare at each other for a few seconds before he talks.
"Try gather your chakra on your fisted hand." He commanded, eyes not living hers.
Sakura blinks once, twice, "Huh?" Sasuke stop in his tracks, as so Sakura.
"Focus your chakra at the tip of your fist, and when you think you got it done, hit the ground." He said, still looking her way but not at her eyes this time. He realized how her deep green eyes has always mesmerised him.
Not really understand what's the point of that, she nods anyway. She hold her hand into a fist and focus her chakra to gather right there, closing her eyes mildly.
That little commotion didn't go unnoticed by their gray haired sensei. He's gotten interested by Sasuke's suggestion and stop reading his Make-Out Paradise, and muted Naruto's loud voice completely.
When Sakura was positive that she's done what Sasuke told her to, she open her eyes and breath in before her body dip down and bring her elbow up and punch the ground, "Shannaro!" She shriek her catchphrase. Sasuke jumped away from her to where Kakashi and Naruto is just in time when a loud cracked sounds engulfed their surroundings.
It happen better than he had expected. The ground cracked in about 2 metres radius from where she's standing.
Sakura looks astonished at the crushed debris, then turn to look at Sasuke who's checking on the ground. And then his gaze met hers, the look of pure excitement and proud on the girl's face caused his smirk makes it way lazily to his lips.
Sakura's eyes turn to Naruto who has the look of pure horror. "S-Sakura—chan, you're scary." she grins at him. And then to her teacher who's gazing at her with an amused look.
"Ahh, did you discover Sakura's ability, Sasuke." Kakashi asks in teasing tone.
Sasuke's respond is expected, "Tch." And then he continues, "I don't think that's enough though. Is there anything she can do with her good chakra control?"
Kakashi look at his favourite student, wondering when did he become so concern about their only female teammate ability, and nods, "Yes. Medical ninjutsu. Though, I have to warn you. It's a really hard thing to learn."
Sakura bounce her way to them, "Medical ninjutsu? That sounds great. Do you think you can teach me, Kakashi sensei?"
Kakashi turns his gaze to his female student and throw her his closed eye smile, "Sure, but I only learn the basic from my comrade years back. You need to learn by yourself for more advance knowledge and jutsu though, I can help you with that. I don't think its too hard for you, since you've got the highest mark on your written test, you'll be needing a lot of reading if you decide to be a medic nin."
If there's something she values herself for, its her brain. She can recite anything straight from the textbook, can understand things just by reading, able to solve any mathematical problem just with one try. With that in thought, she nods, "I'm ready, Kakashi sensei."
Still smiling through his mask, the copy ninja reply, "Good then. Our training starts tomorrow. I'll help you with medical ninjutsu, while these boys will help you with your taijutsu. If you able to do better in taijutsu, I'm sure you're stronger than the boys with that ability of yours."
Sakura's eyes shone with excitement at that possibility, as Sasuke makes his 'tch' noise while Naruto voice out his words of protest.