Life Senjou no Bokura http://www.mangago.me/read-manga/life_senjou_no_bokura/
http://www.mangago.me/read-manga/500_nen_no_itonami/ (one of my faves)
http://www.mangago.me/read-manga/ashita_shinu/
http://www.mangago.me/read-manga/hana_no_miyako_de/
http://www.mangago.me/read-manga/kosha_ura_no_natsu/
http://www.mangago.me/read-manga/life_senjou_no_bokura/
http://www.mangago.me/read-manga/paradise_view/ (sequel of Kimi to Parade)
http://www.mangago.me/read-manga/sorekara_kimi_wo_kangaeru/
http://www.mangago.me/read-manga/tamayura_yuki_ringo/
I'm a crybaby so these are the only ones I could think of. Some aren't that much of a tragedy, but it'll give you that bittersweet feeling
I mean, there have been some BL mangas that literally have given be goosebumps and that I absolutely love because of that. I need some tragic one! I Wanna fall in love and cry with it ╥﹏╥