
does anyone knows the name of the manga where the seme has a fetish for the uke's ass?

I know one... the mangaka of that manga its kamon saeko if im not wrong... but the name of thr manga itself i forgot..

http://www.mangago.zone/read-manga/shiri_fechi_nanka_ni_sukarete_tamaru_ka/
I believe this might be what you're looking for

try this one too:
http://www.mangago.zone/read-manga/kachou_wa_kakko_ii/
what happened at the end? did they stay together or not? i didn't get it!!! someone explain it to me!!!!!!!!!!!!!!!!!
Open ended, so make your own ending. This isn't western religion, so there are no answers except your own. The final line says it all, may your choice leads you to happiness. The author's own little story in the end explains his feelings, I guess.
As for me, I feel that as the way the story was going, this kind of last minute change/how the "villain" wasn't such a bad guy after all thing is a Douche' thing to do story-wise by the author. But if you read the author's other works, he enjoys this kind of Douche' last minute plot twist like a certain famous/infamous movie director. This ending wasn't as bad as that other one. In the end, it feels cheap because all he is doing is pushing all the major emotional buttons, but there is no release in the end, no catharsis. So, it fine to get pissed off.