What if you are insane? If you know it, will you feel uncomfortable or depressed? Or, maybe, you'll think that it's eiser way to live?
Reality is not always like we want it to be. The game is about the man who lives in a really hard reality, because it is full of walking deads. He is the only one in the whole world to be not like others. He is not ordinary, because others are dead.
When you have such problems, you become insane to save yourself alive and feel comfortable. The man has own friends and visual environment.
But how long will you live in illusion? One day, everything will be revealed and the truth will be massive and full of pain.
Kill walking deads, solve puzzles, go through the story. And ALWAYS check how much truth your reality has.