Responses
Im not sure if this is the one. But the seme does mention about replacing all the cells of ukes body
http://www.mangago.me/read-manga/suki_ni_shitaiyo/
the one from dragless sex huh?
Yes, it was this one! Thank you so much (ノ≧∇≦)ノ
Trying to find a series (or possibly oneshot) about this guy who feeds this lover for months/years and his lover finds out that it's because all the cells in the body replace themselves after a certain time, so basically he wanted to be the one who 'fed' his entire body? Hope that made sense, thanks!