Just depressed

It's called "not so simple" not the saddest, but it's the only one I remember

http://view.thespectrum.net/series/not-simple.html

I highly recommend them all. I'll let you know if I think of any others.
http://www.mangago.me/read-manga/watashitachi_no_shiawase_na_jikan/
http://www.mangago.me/read-manga/bokurano/
http://www.mangago.me/read-manga/a_lollipop_or_a_bullet/

thanks gonna start reading now

thanks hope u find more

Manga:
Fullmetal alchemist
Death note
Sakura gari
Nana
Shigatsu wa kimi no uso
Hybrid child
Chrno crusade
Glass mask
Koe no katachi

You can watch these anime too:
Madoka Magica
Code geass R1+R2
Hybrid child (originally a manga but the feels you get watching the anime are REAL)
No 6
Byousoku 5 Centimeter
Kimi no Na wa.
Myself yourself
Ookami Kodomo no Ame to Yuki
Suki ni Naru Sono Shunkan wo.: Kokuhaku Jikkou Iinkai
Hotaru no Haka

Disrespectful bitch

You can also read these:
Sakamichi Appolon
Honey & clover