Itachi was four years old when his mother and father told him he was going to become a big brother.

Apparently, his parents have decided not to find out whether he's going to have a baby brother or a baby sister until he or she was born. So Itachi would only be able to finish the welcoming board he's making for his new sibling in the next nine months. Ah well. That means he has more time to decorate it and make it even better.

"Itachi." Uchiha Fugaku calls to his son while staring hard at a blank piece of calligraphy paper. "What do you think of the name 'Sasuke'?"

Itachi stops his work on decorating the "WELCOME BABY _" sign and stares at his father. "But father, isn't Sasuke a boy's name?"

"It is the name of the late village chief, a name of a great, esteemed man."

"But we don't even know yet if I'm going to have a sister or brother."

"I'm only asking you how you feel about it, son."

"I think it sounds cool." Itachi flippantly says and went back to work. It's pointless to talk more when his father has that tone. What was it that his mother had called him? 'Idiotically stubborn bastard', was it?

"Yes. It is an appropriate name for an Uchiha heir." Fugaku says with relish and lifts a brush and starts working on his calligraphy.

Itachi just ignores his father and wonders whether he should use blue or pink for the flowers he's drawing on the board. He decided to use both. It's going to look even better if it's more colourful.

When his father makes a sound of triumph and lifts a piece of paper with 'Sasuke' beautifully written on it proudly, Itachi also lifts his newly decorated board and looks at it in satisfaction. Now he only needs to ask his mother to help him put glitter on it, and it will be the perfect welcoming sign to have ever been made.

Later into the day, when Itachi was drifting off to sleep, he hears noises that sound like muted yells from his parents' bedroom. He can hear his mother's voice going 'But we agreed to look for a name after the birth!' and his father going 'Sasuke is a perfectly good name!' and 'Don't yell! It's bad for the baby!' 'Well if you didn't bring up this nonsense I wouldn't be yelling would I?'

That night, Itachi dreams of his new sibling smiles and laughs after seeing the welcoming sign he made, and he smiles in his sleep.

It was another peaceful day in the Uchiha household.

Uchiha Sasuke was born on July 23, with a weight of 3.05 kg. A perfectly healthy baby girl.

Before going to visit his mother and his new baby sister in the hospital, Itachi quickly scribbles 'SISTER' on his sign and it is finally done. He bet his sister will like it very much. His mother had said his sign is very pretty to look at, and that if she likes it so much, his sibling will too.

When Itachi arrives at the room his mother and sister are staying, he quickly takes a chair and set it next to the baby cradle. His mother is too busy berating his father in hushed tones for handing in the birth certificate application without consulting her, and that he should've waited and decided on a more girlish name for god's sake, Fugaku. And his father is too busy hard-headedly defending himself with his old 'Sasuke is the perfect name, there's no reason to change it' excuse. So the five-year-old boy takes it upon himself to climb up and have a better look at his baby sister.

Sasuke is sleeping, is the thing Itachi first noticed. The second thing is that her face is really small. Her eyes, her nose, her lips, they are all so small. Her hands, fingers and palm are so tiny too. She also has this cute, small tuft of black hair on top of her head. She might look a little bit like a monkey, but his precious little sister is just perfect. Her cheeks are round like mochi and looked really soft to touch, so Itachi gently pokes it. Itachi watches as Sasuke scrunches up her tiny face and then slowly opens her marble-like eyes. Excitedly, Itachi holds up the sign he is holding on his other hand.

'WELCOME BABY SISTER' is written neatly in colour pencil, the glitter on the letters twinkle under the hospital light, baby blue and pink flowers painted around it.

"Hi, Sasuke. I'm your big brother." Itachi whispers, "I'll be in your care from now on."

Sasuke lets out a soft gurgle, an almost coo, her fingers moving slightly into a fist. Itachi puts one of his fingers in Sasuke's palm, feeling pressure as she clenched it. The boy smiles, feeling warmth spreading in his chest.

Uchiha Mikoto and Uchiha Fugaku looks fondly at their children, their son and daughter. Their beloved, most precious treasure.

Sasuke was six months old when she learned how to roll over. Years later, Itachi would still know the exact month, date, and time it had happened, as he have always diligently filled out his Sasuke-diary whenever anything of importance occurs.

It happened when Itachi is looking after his sister while their mother is preparing dinner. Father is going to be home late, so dinner will only be the three of them. Itachi is doodling while huddled up in the kotatsu while keeping Sasuke, who is comfortably lain next to him, within his field of vision. When he heard a soft 'thump', he looks towards Sasuke's direction in surprise. The baby girl is lying on her stomach, tangled up in her blanket, looking up at him with a bright face. She squirms around, trying to get herself out of the blanket but stops after a moment of struggle.

"Mother!" Itachi calls out to his mother, excitement dripping from his voice and puts down his colour pencil, "Mother, look at Sasuke!"

"Wait a minute, honey. I'm still cooking," is his mother's gentle reply.

His sister is waving a hand at his direction now, and Itachi quickly gets out of the kotatsu to crouch in front of her. He is really, really excited about this. Sasuke is able to roll over already! Maybe soon she will be able to stand, and walk, and play and draw with him! Itachi can't wait.

Itachi is pulled out of his delighted thoughts by a sound he suspects came from his baby sister. The boy crouches down even more, to level his eyes with Sasuke. "Sasuke? Say that again?"

"Nii! Nii!" Sasuke says clearly and animatedly, her hands still reaching out towards her brother. Itachi feels his chest tightened and a grin breaking out. He catches Sasuke's tiny hands in his and leans his forehead on hers.

"That's right. I'm your brother." Itachi says in a low, loving voice, "I'm your nii-chan, Sasuke."

Itachi notes to himself to write down this important moment in his observation diary later. For now, he's just going to snuggle up next to the warm little bundle that is his sister, patiently waiting for dinner together.

(Mikoto is surprised and very disappointed when she finds out she'd missed her daughter's first roll and her first word. She isn't surprised, however, when Itachi eagerly tells her how Sasuke was calling out to him. Her first-born dotes on his sister so much and is practically constantly by her side ever since she was born. Now it's her turn to somehow make Sasuke say 'mommy'. And while she's at it, she will also try to make her daughter call out 'daddy'. She bet Fugaku would cry when he heard it.)

Sasuke was one when she learned how to walk. This time, Itachi wasn't there to see it. He did meticulously write it in his diary, though. He never did fail to put into record every single little thing young Sasuke did.

Itachi have started school that year. Proper school, with textbooks and everything, unlike his time in kindergarten. He's an elementary student now. Finished with clean up, Itachi carries the schoolbag his grandparents had bought for him on his back and says his goodbyes to his classmates. He was just walking up to the schoolgate while chatting with his cousin Shisui when he sees the familiar sight of his mother carrying his sister. Itachi picks up speeed with Shisui behind him, matching his pace, and rushes the last few metres before coming up to his mother.

"Mother?" He starts hesitantly, "Why are you here? You didn't have to pick me up, you know, I was just going to walk home with Shisui."

"Hi Aunt Mikoto." Shisui, ever well-mannered, sends his greeting, "Hi Sasuke."

"Hello, Shisui. Thank you for always looking after Itachi." His mother have always been proper, even with family, Itachi thought. Then she turns to Itachi' "I was just out to get mirin." She holds up a Family Mart plastic bag in her free hand to show him. "I thought I'd drop by and show you something."

Itachi furrows his eyebrows. His mother came all the way to school to show him the mirin she bought? His mother does have her silly moments, but this is just plain strange.

His confusion must be showing through, because his mother just smiles mysteriously and gestures so that both Itachi and Shisui back off. And the she puts Sasuke down, and let go of her hold.

By that time, Itachi knows Sasuke can hold up and stand on her own. He even had the full recount on his diary. But his sister is still wobbly and falls down a lot when she walks on her own, and still needs to hold her brother's or parents' hand to balance her and walk properly. His mother had told him that Sasuke still needs a lot of practice. Itachi spends much of his time holding his sister's hands and helps her wobble around the house.

So it truly is unexpected for little Sasuke, in her cute pink frilly Hello Kitty dress, to walk up slowly but steadily towards him. Her hands are reaching out, and she is calling out 'Nii!' and 'Sui!' along the way. Shisui is making excited and encouraging sounds beside him, but Itachi doesn't pay him any attention, tense and focused as he is on being prepared to catch Sasuke if she ever falls down.

But Sasuke doesn't fall down through to the end and she is laughing when she gets a hold on her brother. Itachi bends a little and loops his hands around his baby sister and gave her a tight hug.

"You did well, Sasuke!" Pride shining through his voice, "You walked!" When Sasuke beams at him, Itachi beamed back. Shisui starts petting Sasuke's head and giving out praises, so Sasuke also gives her cousin a wide, toothy grin. From their closely huddled up position, Itachi can see his mother smiling down at them.

When they get back home, Itachi is going to ask her mother how it had happened. He is going to write it down, filling his Sasuke- diary with even more notes. It had felt a little bit weird, seeing Sasuke walk without him holding her. It had felt like his baby sister is growing up way too fast, way too soon. But his father did say babies grow up in no time, so Itachi let that strange feeling go.

When they all walk home, the thoughts filling Itachi's head are only of the places he is going to take Sasuke to.

(At night, Fugaku lets out another wail in disappointment of yet missing another crucial moment in his daughter's development. Mikoto just laughs at him when he sulks and disregards his suggestion on becoming a stay-at-home husband so that he could watch his daughter more often, their family is not short on money but it's nice to have a stable income to depend on, you daughter-idiot.)