Miiang

None of them actually have a tragedy tag but they make you sad.
If you haven't read this yet. http://www.mangago.zone/read-manga/kyuuso_ha_cheese_no_yume_omiru/ and its sequel http://www.mangago.zone/read-manga/sojou_no_koi_wa_nido_haneru/
They put your emotions in a roller coaster ride. but still has a happy ending.
Also http://www.mangago.zone/read-manga/ikusen_no_yoru/ is a nice one. It gives you heartache but is also heartwarming.
And a shoujo which became very famous due to the anime but if you haven't read the manga or watched the anime then try http://www.mangago.zone/read-manga/orange_takano_ichigo/

Tks so much for your suggestions. I'll try each of stories you said.

You're welcome. Glad to be of help :)

NYNY and Complex. The endings aren't really tragic so much as bittersweet. Especially NYNY. The mangaka basically kicks your heart in the nuts.

Koe no Katachi is an emotional rollercoaster, despite the lack of the tragedy tag. This manga is so intense that the publishers weren't even sure they should publish it. I recommend it 100%.
http://www.mangago.zone/read-manga/koe_no_katachi/

They gave it a tragedy tag? Weird.

I've just finished the 1st and 2nd story you suggested. And it made me cry over and over. It's a sad yet cheerful story that i think is close to reality. Really a good one. Tks so much again.

I can't find the name NYNY. And there're too many mangas with the "complex" titles. Can you give a more specific name?

Tks so much for your help but this story is too long. I barely have time to read now so I want more of a 5 or 6-chapter manga. Can you recommend one? I"ll definitely try your story when I have more times.

Sure. "New York New York" is the full name.

"Complex" has four volumes, so it's probably too long for you.

How could I forget! This one ends happily, but always leaves me feeling dead inside. :D
http://www.mangago.zone/read-manga/bokutachi_futari_ga_koisuru_riyuu/