Magazine writer Hayato Ibuki was chasing the story of the suicide a person who jumped in front of a train in Shinjuku Station. In the middle of his pursuit, he falls onto the platform as if he was pushed by a mysterious black shadow. A mysterious, beautiful woman named Barcia (voiced by Miyuki Sawashiro) saves him by the skin of his teeth, and hands him a suitcase. It was a Pandora's Box that should not have been be opened. Inside was the "Demon Gun Gangour," a tool that can capture and enslave demons and fallen angels. Using this ability, Hayato successfully took on his own demon subordinates. Together with a woman named Rua (voiced by Rikako Yamaguchi), who calls herself an angel, Hayato will pursue the mysteries that occur in various places and find the beautiful woman who gave him the suitcase.