Shintaro is a detective at the Kichijoji police station in Tokyo, Japan. Shintaro works with Yu Nagamine. In his personal life, Shintaro is married to Kaori and has three children. His wife is currently hospitalized. In the past, Shintaro's work as a detective was exemplary, but after his wife became ill his focus shifted to taking care of his family. Arrest ratings at his police station dropped because of this. Shintaro tries his best to balance work with taking care of his family, but it is difficult. Karoi's mother, Yoshie, then offers to take care of the kids.