sad

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

tääolisurulline

I would recommend Endless World, it's a yaoi and it is pretty depressing, but idk if it will make you cry, that kinda depends on you :P

Yatamomo.... seriously read this.
Lovers boy
Cavalier of the abyss (second season story is a mess but the flash back story of the prince was heart breaking.... i was a mess and even when rereAding i was a mess)
....tokyo ghoul? The ending kinda fucked me but it was so pretty


but man...its really hard to cry in mangas.... if you wanna cry alot go watch clannad, code geass and death note.

let the tears flow!
http://www.mangago.me/read-manga/watashitachi_no_shiawase_na_jikan/
http://www.mangago.me/read-manga/usemono_yado/
http://www.mangago.me/read-manga/deep_love_ayu_no_monogatari/
http://www.mangago.me/read-manga/kanai_kun/
http://www.mangago.me/read-manga/oyasumi_punpun/
http://www.mangago.me/read-manga/life/
http://www.mangago.me/read-manga/bokura_ga_ita/

Koi No Katachi

Mars

Blood+ (the anime)

Basara (the art is old but the plot is good)

Bitter Virgin

A Cruel God Reigns (the most depressing one on this list imo)

Hybrid Child

(probably) Lonely to Organdy

Paradise view.

Try not to cry then cry a lot.

Ive got the perfect list for you! http://www.mangago.me/home/mangalist/187262/