If you haven't played the game, you will get a worse version of the story and I highly recommend playing the game. It's a masterpiece. Stop reading this and go play the game. If you loved the game you will love the anime. It has many similarities but some key points are different. For example the anime shows the Pearl Harbour events but switches Anemone and Lily's roles. We also get a little story about Pascal. Episode 1 is just the prologue of the game scene by scenes. The anime goes to ending B but skips some parts (like the alien space ship).