You play as an adventurer having proven herself in the war by defeating one of the Demon Knights, with the help of your companions.
You heard that a strange disease, the Blissful Sleep, is spreading in your childhood town and when your mother told you that your sister has fallen victim of it, you decide to go back home to take care of her.
Once home, you will start investigating the Blissful Sleep and try to figure out the complex situation happening there.