I'm looking for a Yaoi or Shounen Ai manga with two leads who at first don't like each other but slowly fall in love

naruto

I'm pretty sure Naruto is not what you're looking for. However, Kiraboshi Dial may be closer to what you want. You can download it or watch some chapters on youtube.

hey, i also love this kind of yaoi !! like A LOT!!

so, i think you should try this post:
http://www.mangaupdates.com/showtopic.php?tid=17523

amost of the works listed there are exactly what you look foe !! (if not all of them).
I already read more then the half of them, so i can tell you for sure they are good ^^

From there would recommend you the following :

Rival ni Ki wo Tsukero
Koi wa Ichiya ni Shite Narazu
Shortcut Love
Usagi to Ookami no Shinshikyoutei
50 x 50 ***** (one of my fovored of all tomes 😛 )
Get the Moon
Mukizu ja Irarenee ( it very good...but is hard yaou, so be prepared ^^)

This have leads that hate each other at the beginning 😀

You should also try Our Graduation from the volume Tameiki no Ondo by KUNIEDA Saika (last story) ! It's funny and cute 😛

So, have fun !

i laughed too hard at this one

Love Nest: https://www.mangaupdates.com/series.html?id=148220