Does exist any?
No Idea. I hope there is some.
Well these stories has cheating ex-boyfriends that want back the MC but hey choosed thier new love.
http://www.mangago.me/read-manga/motto_aishiaimasho/
http://www.mangago.me/read-manga/yachin_hanbun_no_ibasho_desu/
http://www.mangago.me/read-manga/suki_toiunoni_nazekashira/
~Following
Following
Any good manga where one of the characters cheats or hurts their partner causing their partner to leave them for good. No matter how much they beg for them back?