I'm not a huge fan of zombie games, but the story is okay. I do have a couple of things I'd like to say though.
For one, I don't think that all of your story should be presented to the player before game play takes place.
If the game starts with the player waking up in a straight-jacket, then there is a lot of build up before the player takes the reins and the game actually starts. Instead, you could have the player interact with other survivors as they play and have the main character explain whats going on.
That way the player isn't left out of the loop and isn't bombarded with the story out of the gate. The player can enter the game faster and also feel more immersed into the game world you've created by slowly letting them digest and look forward to the next chunk of the story while becoming more invested in the main character because they're the one taking them through it.
Also, you might want to differentiate the names of major characters a little bit more. Nicolai and Noliuk may not read the same, but as I was reading, it became kind of confusing. I had to go back and make sure Noliuk wasn't Nicolai because I was thinking maybe I had misread the name earlier. What I try to do to help characters feel more unique is to make sure their names start and end with different letters. That way if they are being read about in text form, they have a very difficult time being confused for one another.
But that's just my thoughts on your story.