It actually does. Halfway through it gets dark. What did you expect with a light novel cover like this?
But great insert songs.
The anime starts on a happy note with MC trying to make her happy, but she starts forgetting all the memories she spent as her hair goes redder. It hurts when you are watching knowing the inevitable through hints, and it was darker than we thought it would be. And yes, she forgets everything and dies, there is no miracle like Clannad. Later in the light novel MC also dies.