The 17-year-old human boy Wakamiya learned a shocking secret about him when he was about to become an adult - he was actually the son of the demon king in his previous life. Since the demon world has lost its king now, the people in the demon world are looking for a new demon king under the instructions of the old demon king. As time went by, many different monsters and angels appeared around Wakamiya, and they all had different purposes. Just when the night gradually woke up, that person actually appeared... He awakened his memory, and that person was...