He wakes up in a room and finds a woman, whom he doesn't know standing there. She says that he is the reincarnation of her liege. The Demon Lord who was sealed away centuries ago by the goddess of the land. She tries to give him his memories back but fails and gets upset. Then she decides that to awaken him, she must take him to the places where parts of his sealed power should be. Threatened by her, he follows her. In the first dungeon, he saves a priestess who thinks he's the Messiah coming to save the lands from evil... (Source: OLF, edited)