The game starts at the top of a rusty metal spike. You have no idea where you are or what you have to do, so a little exploring is in order. Nearby, you find Frfr, the cursed angel. He (or she?) tells you that "The Opening draws near. If you are able, it is a great opportunity for one who is pure of heart to cleanse our little world of evil."
So, there you go. Sounds like a mission, does it not?