Itachi had been adamant about keeping his promise.

Protect your sister, alright, Itachi?

He'd take his promise to the grave if need be.

I promise, Mother

A promise of a lifetime, some call it. Well, he'd agree.

Because a lifetime shall be his endless promise.

Age 8.

"Itachi! Teach me something!" A young voice shouted excitedly, coming closer and closer to where he sat in the dining room.

Itachi looked up and smiled, watching as a little raven-haired girl came shooting around the corner.

"What? No 'I'm home, Itachi!'?"

"Hmph! I'm not a little girl anymore! I'm a ninja!" The girl huffed and crossed her arms, tilting her little chin up in defiance.

Itachi chuckled a little. "That you are, my sweet little Sasuke, that you are." He patted her head and poked her forehead.

Sasuke staggered back, holding her forehead, and glared at Itachi. "I said I'm not a little girl anymore! Stop doing that to me." She pouted, looking down. "I'm a ninja…"

Itachi sighed and leaned down, looking into her eyes. "Well, could you at least be my little girl? Just for now? I'd really appreciate it." Itachi smiled.

Sasuke huffed and looked to the side, slowly nodding. "Okay…"

Standing back to his full height, Itachi clapped to get Sasuke's attention before he announced:

"Alright, now who wants to learn some ninja stuff?"

"Me! Me!" The little girl shouted, bouncing up and down.

"Let us head out, then," Itachi instructed, pointing towards the back door.

Sasuke immediately ran to and out the back door a little faster than Itachi had expected. Hmm, fast for her age. She must be at the top of her class in ranking, I'm sure of it.

Itachi walked towards the door, following after Sasuke. Just before he stepped out, he turned towards the wall on his right and looked at the framed-picture hanging there of his Mother and Father.

As you said, Mother, they really do grow up too fast

Age 10.

Itachi was curious.

Sasuke had been sitting at that table for three hours now, writing… something.

She would often, at times, blow out a breath of frustration and crumple up the piece of paper she was working on, clumsily tossing it over her shoulder and, to Itachi's surprise, in the bin behind her.

Without looking up.

And it landed every single time.

He was immensely impressed by that display, but that wasn't what was important right now. It was what she was writing that was.

Itachi snuck up behind her and tried to sneak a peek over her shoulder, only catching a glimpse of a single word before Sasuke covered it with her arms. Itachi's eyes narrowed.

Naruto

"Ugh, what do you want, Itachi? Can't you see that I'm busy?" Let out Sasuke, annoyed that her brother was trying to peek at her letter.

Itachi simply smiled and backed away, turning around and immediately gaining a serious glint in his eyes.

Naruto

Itachi would like to know who this Naruto fellow is.

XXX

"Hello."

Naruto squeaked out a squeal and turned around in the bush he had been hiding in, looking around and, to his confusion, not finding anyone.

"W-who's there!." He demanded.

"You are Naruto, correct?"

Naruto continued to look around, trying to find the voice that was speaking.

"Y-yeah. What's it to y-you?" Naruto squeaked out, the fear in his voice obvious.

Itachi finally revealed himself from the shadow he was hiding in, walking slowly towards the quivering boy. "Have no fear, boy, you are not in trouble." For now.

Naruto looked at Itachi and noticed something weird-cool-about his eyes.

"Hey! What's up with your eyes. They look so cool!" Naruto let out, admiring Itachi's Sharingan eyes.

"That is not of relevance. What is, though, is the relationship you have with Sasuke Uchiha."

Naruto looked surprised for a second before he grinned and said:

"Oh, Sasuke? Yeah, she's my best friend!" Naruto then looked down and spoke in a quieter tone, almost sounding sad. "More like my only friend…"

Itachi raised an eyebrow at this.

"Well, be sure to treat her right," Itachi said. He then gained a darker tone. "Or you will be paying severely, got that?"

Naruto nodded nervously, gulping.

"Good."

The next thing Naruto knew, he was now in the same position he was hiding in prior to meeting Itachi, now looking out towards an exit of a building.

"Huh?" Naruto said, looking around, confused.

He didn't have much time to think about it, though, when a loud voice was heard.

"Naruto! I know this was you! Come here right NOW!"

Naruto jumped and looked towards the exit of the building, now seeing a furious Iruka covered in glue and glitter.

Naruto began to giggle and, looking once more over at his ridiculous-looking sensei, began to sneak away from the crime scene.

Prank successful!

Age 12.

Itachi couldn't believe he was doing this.

But it had to be done.

It was a way to keep Sasuke safe, after all. Things like this must take precedence above all else.

"What are we doing here, Itachi?" Grouched an annoyed-looking raven-haired girl. "This is my day off, remember? I just wanna sleep today. Not stand here at a market of all places, loitering."

Itachi smiled down at his little sister and tapped her forehead. "Now, now, Sasuke. As I said before, this is an important lesson that you must know."

Sasuke was now at that age where she would be curious about… boys. Itachi knew it was coming, and he had tried preparing for it, but they just grow up so fast.

"Oh, yeah? And what would that be?" Sasuke said, looking bored, as always.

"So..." Itachi began, suddenly feeling nervous. He coughed into his hand and just got straight into it. "You're at that age where you must be curious about boys, and I just-"

"Okay, let me stop you right there," Sasuke said lamely, holding up her hand, interrupting him. "Is this what this is about? Boys? Seriously?" Sasuke said, groaning and slumping her shoulders. "I'll have you know that no, I'm not in the least bit curious. At all."

Sasuke began to walk away, heading in the direction of their home.

Itachi just stood there for a few seconds and contemplated what had just happened before he shrugged, following after Sasuke.

Must be a late bloomer

Age 14.

Now is the right time, he'd say.

Sasuke is 14 now, growing up too fast for his liking, and she'd begun growing in… areas Itachi will not speak of.

Boys will be flocking towards her in no time, he was sure of it. They'd get their seedy little hands on his precious little sister and who knows what those mongrels would do to her.

But, he couldn't keep an eye on her all the time so, like two years ago, at the market, he had come up with a compromise.

He just needed to educate Sasuke a little bit, that's all.

"Again, Itachi?"

"Yes, again, Sasuke. And you are going to listen to what I have to say this time, okay?"

Sasuke just sighed. "Yeah, whatever, sure. But, just so you know, I'm still not 'curious'"

Itachi smiled down at Sasuke. "That's fine. It could come in handy, you never know." He then coughed into his hand and pointed towards a boy, maybe two years older than Sasuke, helping an elder lady with her groceries. "Okay, Sasuke, do you find that boy acceptable material? As in dating material."

Sasuke looked over to the boy helping the lady with her groceries with bored eyes. "The actual boy? Or his actions?"

"His actions, of course."

Sasuke shrugged, looking like all she wanted to do was lay down and sleep. "Sure, I guess."

"What about that one?" Itachi asked, pointing at a boy who looked to be in his late teens, flirting with a group of girls. The girls would just nod at him and tune him out, obviously not interested, but he didn't seem to notice and continued.

"Obviously not. He looks like an asshole."

Itachi nodded, pleased.

"Okay. What about that one?" Itachi then pointed at a man helping a woman up, her tripping all of a sudden.

"Uh, sure, why not?"

Itachi began shaking his head. "That would be incorrect, Sasuke." He then pointed to them again. "Look a little closer."

Sasuke just sighed and looked back at the duo, squinting her eyes. She noticed the guy staring at the woman's cleavage with an intense gaze.

"Ah, now you got it," Itachi said. He raised his index finger and stated: "That man is only doing what he is doing not out of the goodness of his heart, but out of the selfishness of his own desires."

Sasuke nodded, starting to get the lesson now. But still thinking of it all as pointless to her.

That went on for an hour before they returned home, Itachi appearing to be satisfied with how things went.

Age 16.

Itachi was on his way home, bringing all the groceries he had just done. He was preparing to cook Sasuke's favourite dish.

Sasuke has been coming home a lot less frequently now. Whether that be because of her missions or… something else had yet to be seen.

Itachi pulled the key out of his pocket and opened the front door to their house, stepping in and closing it. He went about putting the groceries away when he heard a thud from upstairs.

He paused and looked up. What was that?

Shrugging, he went back to the task at hand when he froze at the sound of a voice.

"Ahh, Naruto! Not so hard, you idiot! It's too big, pull it out. Quickly!"

His little sister's voice.

"AHH! I'm sorry, Sasuke! Oh my god, why is there so much blood!"

The voice of a boy. A vaguely familiar one.

"Duh, that's obvious. That's what happens when you get penetrated, dumbass!"

Itachi literally disappeared from where he was standing, running up the stairs and barging into his sister's room, breaking her door down in the process.

"What the HELL is going on in here!" Itachi shouted, eyes blazing red.

Naruto and Sasuke looked up, surprised at being interrupted.

"Itachi?" Sasuke said, looking at her brother strangely. "Why are you shouting?"

"Because-!" Itachi started only to stop when he took in the full picture.

Sasuke was on her bed, laying down, a massive clever lodged into her thigh and coming out the other side. The boy, Naruto he assumed, was attempting to pull it out rather roughly, causing blood to spray everywhere.

Itachi faced palmed his face. Of course

"Alright, move out of the way, boy."

Age 18.

It was going to happen eventually, he supposed.

Sasuke was a desirable girl, even he could tell. He didn't really want to think about it, but she had… assets that were in her favour.

So it was only a matter of time before she caught the attention of a boy and, in turn, her attention.

Now she was in a relationship and had a boyfriend.

Naruto

And, apparently, they had caught the attention of each other long ago, when they were in the academy together.

That name bought a nostalgic smile to his face, thinking of the boy.

Meh, he could live with that boy being with his sister. He's not a bad kid. He'd actually unconsciously been rooting for them this whole time, he realized.

But, why the hell are they getting married three months after getting together!?

"Be sure to treat her right," Itachi said. He then gained a darker tone. "Or you will be paying severely, got that?"

Naruto nodded nervously, gulping.

"Yes, sir. Always." He managed out.

Sasuke was sitting off to the side, covering her face with her hands in embarrassment, groaning. "Seriously, Itachi? That was not needed, at all."

Itachi just smiled and walked towards his little sister, poking her forehead.

"Just making sure."

They grow up so fast