Oh! Maybe the MC gets infected at the start of the VN, and it slowly progresses throughout the game. If they're with a group, they could choose to hide it, but as the infection grows, they start to understand the zombies and communicate with them? Maybe they keep running into a particular zombie, and it could be a love interest, and have a human love interest too to choose from? Could have multiple endings like telling the human LI about them turning, infecting the human LI, or choosing the zombie LI instead, seeing that it's "not that bad" sorta deal.