I recommend this one. if you search a bit you find se- and prequel then you'll know why the seme was an .....(beep) and he will also find his luck
http://www.mangago.zone/read-manga/sabita_yoru_demo_koi_wa_sasayaku/
this is a bit similar to sabita...... but the focus is on the future seme
http://www.mangago.zone/read-manga/ano_hi_no_kimi_wo_dakishimeta_nara/
here uke has a boyfriend but he will fall in love with the new one (dont tell ya why his 'now' boyfriend is an shitheat)
http://www.mangago.zone/read-manga/love_and_baseball/
mhh does it fits? uke has one night stand for comfort (was dumped by bf, later he wants him back but we have an example for bastard seme)
http://www.mangago.zone/read-manga/jounetsu_no_young_man/
Okay okay so I want a yaoi couple
but here's the thing( ° ʖ °)
I WANT A SUPER EMOTIONAL BREAKUP
NO GET TOGETHER AFTERWARDS
JUST SOMEONE FINDS THEMSELVES A BETTER MAN.
But I don't want the breakup to be of reasons that they can't be together and stuff, NO. REASON GOTTA BE THAT ONE OF THEM WAS A BITCH.
Please and thank you!ヾ(☆▽☆)