These are not THAT sad like tragedy sad but bittersweet maybe
http://www.mangago.me/read-manga/bokura_ga_koi_wo_ushinau_riyuu/
http://www.mangago.me/read-manga/see_you_later_mermaid/
http://www.mangago.me/read-manga/itsuka_tomodachi_ja_nakunaru_to_shite_mo/
http://www.mangago.me/read-manga/kowagaranai_de_soba_ni_ite/ kinda?
http://www.mangago.me/read-manga/kimi_no_naka_ni/
http://www.mangago.me/read-manga/love_letter_sakai_kunie/
http://www.mangago.me/read-manga/first_bite/
i hope you can handle these
http://www.mangago.me/home/mangalist/760720/ my list just in case you want more
Sad unrequited love yaoi recommendations
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