http://www.mangago.zone/read-manga/hana_no_miyako_de/
Miyamoto Kano has a few stories like that. I seem to recall that her Hydra series features a particularly tragic loss.
Hyrdra is sooo T_T I stopped reading all manga from the same author after that
http://www.mangago.zone/read-manga/count_cain_godchild/
Let me check. I'm not sure if these stories really fit, but this one is more bittersweet than tragic: http://www.mangago.zone/read-manga/koi_o_kataranai_kuchibiru/
And this one is resolved in a very cute (and implausible) fashion, but the first couple of chapters pack a real emotional wallop:
http://www.mangago.zone/read-manga/abiru_junjou/
So, I guess it depends on what you're looking for.
I just read yesterday one of her works it's about an editor and writer. The editor first lover gang raped him and abused him sexually and emotionally blah too heavy stuff even if the manga ends nicely still it leaves me riled up. Definitely if i'm in the mood of reading something sad I'd go to that writer directly
I rarely read stuff where they wont end up together lol but here is one :
http://www.mangago.zone/read-manga/matsugo_no_yume/
Bittersweet is absolutely okay. i'm just in the mood of reading a sad relationship bcause suddenly i rmembered the day when i broke up with my gf. Well same-sex relationship aren't allowed so we just eventually breakup bcause of certain circumstances.
Anyway manga like castle mango, ogawa chise's or kyuugou's will do. I always love the stories they made. Thank you so much.
[[Ƨ✿S]] Heartbreaking with Sad ending or They can't be together.
http://www.mangago.zone/read-manga/the_inheritance_of_aroma/
http://www.mangago.zone/read-manga/shiosai/
http://www.mangago.zone/read-manga/mahoroba_no_hibi/
http://www.mangago.zone/read-manga/sakura_gari/ - Open end, up to readers to interpret
http://www.mangago.zone/read-manga/hana_no_miyako_de/
http://www.mangago.zone/read-manga/hybrid_child/
http://www.mangago.zone/read-manga/the_king_and_the_attendant/
http://www.mangago.zone/read-manga/eien_no_aida_ni_miru_yume/
http://www.mangago.zone/read-manga/kimi_no_kanaderu_hikari/
http://www.mangago.zone/read-manga/kosha_ura_no_natsu/
http://www.mangago.zone/read-manga/otoko_benten_enbun_roku/
http://www.mangago.zone/read-manga/setsuka/
http://www.mangago.zone/read-manga/the_secret_agreement/
http://www.mangago.zone/read-manga/othello_yaoi/ - Ch.4-5
http://www.mangago.zone/read-manga/ano_hi_seifuku_de/
http://www.mangago.zone/read-manga/kimi_wa_machigatteiru/
http://www.mangago.zone/read-manga/itou_san_kuraka_sui/
http://www.mangago.zone/read-manga/blue_nathanael/
http://www.mangago.zone/read-manga/the_master_and_me/
I just pick the sad end from my list.
http://www.mangago.zone/home/mangalist/215/
http://www.mangago.zone/read-manga/itou_san_kuraka_sui/
http://www.mangago.zone/read-manga/sakura_gari/
http://www.mangago.zone/read-manga/the_inheritance_of_aroma/
http://www.mangago.zone/read-manga/yami_bl/ (ch.1,9)
http://www.mangago.zone/read-manga/eien_no_aida_ni_miru_yume/
http://www.mangago.zone/read-manga/matsugo_no_yume/
http://www.mangago.zone/read-manga/teirui_makura/ (ch.3,4)
http://www.mangago.zone/read-manga/natsujikan/ (ch.1,2,5)
any yaoi with sad ending where They can't be together because some circumstances?
Shounen ai or shoujo ai is also okay
Thanks in advance