Shoujo manga/manwha with kind/brown-haired ML chosen over black-haired guy??
Can only think of these, all ends with the lighter color haired guys
https://www.mangago.me/read-manga/chihayafuru/
https://www.mangago.me/read-manga/hirunaka_no_ryuusei/
https://www.mangago.me/read-manga/kageno_datte_seishun_shitai/ (vol. 7)
https://www.mangago.me/read-manga/hatsukoi_jihen/
https://www.mangago.me/read-manga/i_want_to_break_up_with_the_man_i_love/
No bdsm
i just finished this one https://www.mangago.me/read-manga/soft_and_squishy/
https://www.mangago.me/home/mangalist/2633769/
Check out this list, it has big/manly uke, you can find something here~

I mean you really feel the romance. It shouldn’t just be hot guy obsessed or in love at first sight. Both of them shouldn’t start out with feelings. And there’s a general tension/awkwardness bc they’re conscious of each other.
Blue sky complex
Thanks for the rec!! The story is really wholesome so far. Any other manga u know that’s like this?
Not similar in plot (at all) but has the no feelings slow burn you asked for:
Turning
Oh scratch that I have a better one if you haven’t already read
Happy twogether
It’s more like what you want