Not all are hardcore, but I saved manga I thought had a good story line, here:
http://www.mangago.zone/home/mangalist/56720/
http://www.mangago.zone/home/album/8942/
here's a few specifics in my list that I think are hard core:
http://www.mangago.zone/read-manga/karamete_de_kudoite/
http://www.mangago.zone/read-manga/sex_pistols/ (I don't know if this is mainstream or not ...)
look over my erotica list if you have read those http://www.mangago.zone/home/mangalist/50912/
oh wow thank you guys ヾ(❀╹◡╹)ﾉ~
so do any of you guys know any yaoi manga that is like sweet, loving but have hardcore sex? its better if it isnt mainstream cos prolly ive read it