A people-pleasing enginner, Aoki Soumá, had an accident with his colleague, Tatekawa. Upon awakening, he was in an unknown country called <Baiyāng>. There, a middle-aged man calling himself Yi Yan told Soumá that he has a rare level of <Yang> (basically, erotic power). Soumá, who has suddenly become the saviour of Baiyāng starts his journey with Yi Yan to visit Philosophers to gather the power of Yang and protect the country from the Demon King <Kyusei no Tsuki>.