Play the Visual Novel. Seriously. It is significantly and way better. As well as 18+ real content. Its amazing really for a zombie apocalypse game. And the art is pretty insane too, the web version is still good but the visual novel technically improve everything upon it and made it better.
sadly its not available in English yet so hopefully someone will pick it up someday

I gave it a really low rating (1) because of personal preferences. For starters, there are necrophilia, forced/blackmail sex (sorta rape), and the like. It supposedly have a H-game too, which explains why there are so many sex scenes. But the protagonist is just a piece of shit. He is 140% selfish and self-centred, detestable. Sorry, but at the end of the day, I like hero or anti-hero protagonists, not this kind of shit. He's not a world saver. He's not an antagonist, like trying to side with zombies. He's just selfish and don't care for anything but himself, use kids and blackmail teenage girl.