During a trip for employees of Mitsuto Shoji, one of the largest trading companies in the country, a murder case unexpectedly occurred. With the murder of the director as an opportunity, the company's internal problems that had been concealed until now were accidentally made public. Haru plays the protagonist, Ikuko Okada, who has a simple and gloomy personality but strong work ability. Ikuko became interested in the incident and began to investigate alone, but soon she was targeted by the police. Kimura Yoshino plays the section chief Mikami Tsuruko, who witnessed the director's affair during the trip and conducted case reasoning alone in the private diary on SNS.