In Yume Nikki, players take the role of Madotsuki, a girl who hardly ever leaves the house, and instead, dedicates herself exclusively to watching TV and playing video games. She also suffers strange nightmares every time she goes to sleep.
So every day you can either turn on the TV and watch it, something that has no effect, or play video games, which is pretty boring, or go to bed and sleep... this will put you into the nightmares, and where the real game takes place.
While sleeping, the small Madotsuki apartment becomes a whole world of strange scenarios where you can explore the troubled mind of your protagonist (or so it seems).
Within each of the more than twenty 'worlds' that you can visit while asleep, it is possible to buy a 'fact'. These allow you to progress through the game and learn more about what is happening. However, the reality is that you will never have a concise picture of what is happening, but it is instead left to the player to interpret the events.
Yume Nikki is a truly disturbing horror game that has thousands of followers and fans for good reason: it offers a really interesting gaming experience that goes far beyond its somewhat neglected graphics.