I don't really remember such thing ever happened to me. But I have fond memories of reading Abe Miyuki's works: not only the beautiful characters but also the plot touched my heart.
some yaoi and shounen ai:
-"Yuki Iro Machiboke" ( http://www.mangago.zone/read-manga/yuki_iro_machiboke/ )
-"Links" ( http://www.mangago.zone/read-manga/links/ )
-"Long Vacation" ( http://www.mangago.zone/read-manga/long_vacation/ )
-"Hatsukoi Wa Gunjou Ni Tokeru" ( http://www.mangago.zone/read-manga/hatsukoi_wa_gunjou_ni_tokeru/ )
and two ongoing manga:
-"Leopard Hakusho" ( http://www.mangago.zone/read-manga/leopard_hakusho/ ) *I know it's not very heart warming, but the second story has one really touching moment for me (▰˘◡˘▰)
-"Owaranai Fukou Ni Tsuite No Hanashi" ( http://www.mangago.zone/read-manga/owaranai_fukou_ni_tsuite_no_hanashi/ ) *you probably know it already, but if not better read the prequel first ( http://www.mangago.zone/read-manga/gosan_no_heart/ )
Manga that has such a happy scene it touches you so much you cry? Literally. At least, a little bit teary eyed. Romance or any genre is fine. BL and straight is ok too.