Just like most games they don't need a million mechanics, just a couple of strong ones with a decent skill ceiling. Porn will get me in, but it won't make me stay.
Side note: If there's only one or two choices and most of the game railroads you, why is it labeled a VN? I'll give a pass for new...
I don't know of any games that mixes actual fighting (punching, stabbing, etc) with sex. Would love to play some. My inner sadomasochist craves to see some chick riding her partner while pummeling him with a metal pipe or something or a fresh amputee covered in bite wounds getting their ass...