It was supposed to be my mission to kill you so how did I end up falling in love with you? Miya Atsumu who's a secret spy of Division of Intelligence located in Ichigaya district in Tokyo was assigned with a mission to be a hitman of the most popular yakuza group in Japan. Sakusa Kiyoomi, the new head of Sakusa-kai, was forced to replace his father to continue the business. Did he made a mistake trusting Atsumu or would this be a new start to change his view in life?