Meeting Tsuna
You met Tsuna when you were 4 years old. He lived across from you, but you met him at the playground nearby.
Maybe it was because you often stayed home, glued to the TV, watching all the shounen (action and adventure, fighting - a genre) animes. You weren't too into shoujo (love and romance - another genre) animes. The shounen ones had some shoujo elements, but you just didn't like sappy love stories. [A/N: Kids can watch shounen too! As long as it's not too gory and stuff...]
You did go for kindergarten, but Tsuna went to a different one.
Back to when you met Tsuna.
Your mums were surprisingly friends. They had known each other for quite a while now, but both had been busy with work and taking care of their respective children.
"(Your name), this is mama's friend, Sawada-san. And this is her son, Tsuna-kun. Be polite and say hi." Mama instructed.
Being the good girl you were, - you would also get someone to play with - you greeted him.
"Nice to meet you, Tsuna-kun! I'm (your name)."
"H-h-hello, (your name)-chan." He stuttered.
He was hiding behind his mother's legs the whole time - whereas you stood beside your mother. You wondered why he was so scared.
"Mama, why is Tsuna-kun scared of me?" You asked, quite sad that he wasn't being friendly towards you.
"Tsu-kun! Be polite with (your name)-chan." Sawada-san said, nudging him forward.
"Tsuna-kun isn't familiar with you, he's shy, not scared. You can go and play while I catch up with Sawada-san." Your mother explained, squatting down to adjust your hair.
"Oh, ok. Tsuna-kun, wanna go play?" You were at the playground, and it would be a waste to miss the opportunity to play.
You extended your hand towards him.
He looked at his own mother; Sawada-san smiled at him and urged him forward again.
He hesitantly took a few steps forward, reaching out to you. Finally, he held your hand.
"Let's go!" You said happily, skipping off towards the slide, with Tsuna at your side.
After a few minutes or so, Tsuna finally warmed up to you and the both of you played happily.

Before heading home, Sawada-san invited you over to their house for a play date the next day. Your mother agreed and also invited Tsuna over to your own house for another play date the day after that.
You were so excited! Tsuna, on the other hand, smiled happily as you jumped for joy.
You guys were going to have so much fun!

The play date over at Tsuna's house was really fun. Both of you played with the toy robots Tsuna had.
"Woah! You have so many robots!" You exclaimed with glee as Tsuna revealed the extent of his collection of toy robots to you.
Tsuna just smiled, happy that you liked robots as well. After playing, you had to go home for dinner.
You felt sad, you still wanted to play some more. But in hindsight, you still had another play date with Tsuna the very next day.

The next day, Tsuna came over. You two had loads of fun playing with some of the toy figurines and blocks you had.
"Tsuna! Let's build a house!" You suggested.
"Okay!" He was quite enthusiastic about it.
Both of you marveled at your creation once you were done. Man, did it look fantastic.
Sadly, it was time for Tsuna to go back, and once again, you were sad. So was Tsuna, he seemed to be quite down.
"Don't be so sad, (nickname)-chan can always go over to Tsuna-kun's house!" Your mother offered.
"Can I?" you asked in wonder.
"Yes, yes you can." Your mother answered, smiling at your newfound happiness.
After celebrating for a while, your mother took a photo of the both of you with the house made of toy blocks.
Then Tsuna went home. Even though he was just across the street, you already felt lonely just without his presence beside you.

From then onwards, you kept on going to Tsuna's house to play (after you finished your homework), and just watch him complete his. When he finished his homework first, he would then come over to your house to play.

[A/N: I think kindergartens give homework. I have totally forgotten my kindergarten days. Let's just assume it's some colouring and writing the different kanji (Japanese characters).]

Most of the time, it was the former (you going over to play and wait for Tsuna).
It became such a routine that if your mum needed you, she would just call the Sawadas'; likewise for Sawada-san.

After a while, Sawada-san told you to call her 'mama' as well. You then opted to call your own mum 'Kaa-san' (mum - in Jap) instead.
At first, your mum was quite puzzled about the change, but accepted it nonetheless.