I'm looking for romance mangas with characteristics below:

-ongoing is okay; preferably completed (and not too long. it's ok too though)
-preferably a sad ending; the lead got rejected or unrequited love or they did end up tgt but broke up somehow
-not ecchi/hentai
-it tells how the lead fall in love, not "A has a crush on B" at the start of the series this is the main point

i'm okay with BL/GL.

thanks in advance!

The closest I can think of is Love Calendar

My current top 3:
Fullmetal Alchemist
Pandora Hearts
3-gatsu no Lion