Not sure, but the only Ass fetish mangas I know are :
http://www.mangago.zone/read-manga/shiri_fechi_nanka_ni_sukarete_tamaru_ka/
http://www.mangago.zone/read-manga/suki_dakara_itte_hoshikunai/
http://www.mangago.zone/read-manga/majouu_school_days/
The third one isnt really focused on the uke's butt, but it has a similar setting(?)
Thank you! That's the one
Since yesterday, mangago community's obsessed with beautiful / big butt. I saw ~4 requests already. HA+(≧∀≦)
IKR lol. bubble butts are trending
Looking for a certain manga that I can't remember the name of. where the uke has a big butt, and the seme is obsessed with his butt. I'm pretty sure the uke also acts kinda like a tsundari. In the beginning of the manga, the uke gets molested on a train and the seem saves him, but accidentally starts touching his butt too