jia

http://www.mangago.zone/read-manga/life_senjou_no_bokura/

http://www.mangago.zone/read-manga/kimi_ni_ienai_koto_ga_aru/

Back in time to you, it's shorter and sad. Diamond Dust, It's not as good as other stories but still pretty sad. Days Of Hana, or Hana Haru I think is the title on this site is very sad don't be fooled by the lack of tragedy tag. Jack The American Ghost is kinda sad. And Psycho is sad too if you want more of a psychological story.

Here!: http://www.mangago.zone/home/mangalist/795299/?filter=&page=2

http://www.mangago.zone/home/mangalist/1090460/

http://www.mangago.zone/read-manga/silent_lover/

http://www.mangago.zone/read-manga/blue_lust/

http://www.mangago.zone/read-manga/blue_lust/

Life senjou no bokura
http://www.mangago.zone/read-manga/shounen_no_kyoukai/ (the story of the side couple, this is also abo)
New York new York

http://www.mangago.zone/read-manga/complex_manda_ringo/

http://www.mangago.zone/read-manga/momentum_park_ji_yeon/

TEARJERKER
http://www.mangago.zone/home/mangalist/636848/
list is a collection of
 • happy ending
 • bittersweet
 • sad/tragic

i recommend this for quick read
#021  http://www.mangago.zone/read-manga/hate_no_kouya_de_vacances_wo/
#031  http://www.mangago.zone/read-manga/the_specific_heat_capacity_of_love/

You can check the comments section if you want to know which mangas have happy/bittersweet/tragic ending

Follow the list to be updated. And if you liked the mangas/manhwas I included, please do recommend. Enjoy~ (人 •ᴗ•)