The story is split into two stages, two different worlds. On one side is an ordinary town very similar to ours. Our heroine, Mari, lives a very normal life as a student along with her best friend, Kotone.

However, her world is suddenly attacked by monsters from another world. Mari learns she can resist miasma coming out from the other world and save her own world by putting a stop to the monosters in their own world. Learning that, she decides to head off into the new world as a transforming heroine, Lilium, to bring her world back to normal.