nipple play
https://www.nicoobook.com/p/1183450 raw but i think it fits with what you're looking for lol
http://www.mangago.zone/read-manga/hitotsu_futatsu_himitsu/ first couple
http://www.mangago.zone/read-manga/go_houbi_chikubi/
not obsessed uke/seme but you can't help but stare lol
http://www.mangago.zone/read-manga/hard_x_heat_x_heart/ dude
https://toonkor.blue/비누-줍지-마세요
http://www.mangago.zone/read-manga/tongari_aikouka/ and it's reversed nipples kink hahaha
Honto yaju
please recommend me a Yaoi where the seme or uke is obsessed with his partner's nipples or "boobs"