Centers around a disturbing murder case that occurs during a company trip. In the wake of the incident in which the company’s general manager is killed by someone, unexpected internal problems are revealed that had previously been thoroughly concealed to this point. Matoba Ikuko is a plain, gloomy and unfriendly general worker, but her work is fast and accurate. She becomes interested in the case and decides to lead her own investigation. Mikami Tazuko is a hardworking sales manager who witnesses her manager’s affair while on the trip and begins to develop her own theories through her private social media diary.