Sad manga recs?

They are all bl:
The specific heat capacity of love (one shot but hurts...)
Birthday
Spring snow
Life senjou no bokura(don’t be fooled by the start)

If you're ok with some yaoi/shounen ai:

http://www.mangago.me/read-manga/banana_fish/

http://www.mangago.me/read-manga/10_years_where_i_loved_you_the_most/

http://www.mangago.me/read-manga/incidentally_living_together/

Not sure is the other links popped up, if they didn't here ya go ( They are bl)
http://www.mangago.me/read-manga/incidentally_living_together/
http://www.mangago.me/read-manga/10_years_where_i_loved_you_the_most/
http://www.mangago.me/read-manga/december_rain/

http://www.mangago.me/home/mangalist/760720/

At the End of the Road,

http://www.mangago.me/read-manga/sora_o_daite_oyasumi/, december rain (▰˘◡˘▰)

Supernatural Tragedy: http://www.mangago.me/read-manga/hatsukoi_losstime/

Extreme Slice-of-life Fantasy:
http://www.mangago.me/read-manga/sousou_no_frieren/

I may not be too helpful but I hope I could put a couple on your list??