I liked the character busts used in the cutscenes and the battle tracks you used for this game. However, the rest of the game felt too stripped down, like Harold having one attack and not having any options other than using the skills assigned to each character. However, I think the story is where the game suffered the most. It lacked context and lacked any sort of impact.
My suggestions of how the events could have played out: Harold and his friends enter the dungeon where the goddess was, and state how Demon King has affected their home or world. Then go through the dungeon and face the Goddess of Darkness. Then they get the sword and face the Demon King. Then when the King is killed you could have Harold take over Harold and he becomes the new demon king or when they try to return it the sword disallows Harold to leave so they have to destroy the sword to free Harold.