To me its like a restaurant that someone build next to already existing one. That existing one is porn doujinshi I saw a bunch of months if not years ago - dude finds himself in the middle of zombie pandemic - has suicidal thoughts and decides he fill fuck the cutest zombie girl around him - find out in the way that he is also infected, but instead of becoming full out zombie, he "mutated" into a "sperm healer" of sorts - aka if he cums into the zombie girls - they slowly gain their senses back, thou their old memories/self worth is lost or something IIRC aka they become like a mix of a new person and old one - with zombie super strength and stuff. Dude just runs around afterwards and fuck any girl he finds worthy of fucking, but cream-pies only the best ones. Finds few human girls to fuck "and protect from the virus" too. No much of a "plot" in it yet, but while skimming this one through I had like that lingering feeling its a blatant copy - thou one where someone changed enough to make most people not see it as a copy - thou in my eyes it became a bit worse in the process especially with the kinda spineless wuss MC.