
If you havn't already read this, one recommendation for a BL with slow romantic development is
http://www.mangago.zone/read-manga/koi_to_wa_yobenai/
It's a nice slice-of-life bl manga with a satisfying ending. (▰˘◡˘▰)

Also if you're okay with reading BL novels, there are English translations of some really good ones by Konohara Narise with sorta slow romantic development (e.g., utsukushii koto and hako no naka). However, both are slightly serious (esp. Hako no naka), but fortunately have happy endings ٩(๑❛ᴗ❛๑)۶
I could post links here if you'd like?
P.S. The manga Castle Mango by the same author is good too (●'◡'●)ノ

It's one of my favs.! Glad I could help (⌒▽⌒)
Haaaiii... Can anyone recommend some BL mangas where the main characters don't immediately fall in love with each other. Maybe with the kind of development in Ameiro Paradox but slower is also good.
Also, if there are any recommendations (BL as well) where the uke starts with an unrequited love for the seme. Thanks!