Detective Zenji Kenki of the Tokyo Metropolitan Police Department's First Investigative Division has an unusual habit: whenever he considers a case, he begins with “if.” A lover of puzzles and deduction, Kenki is determined to solve difficult cases within 24 hours. His partner, detective Sara Tsurumoto, serves as both his colleague and watchful supervisor, often trying to keep his enthusiasm under control. When Kenki attends the wedding of a former colleague, a torn wedding dress and the murder of the groom's father turn the celebration into a complex investigation involving hidden secrets, conflicting motives and unexpected acts of kindness.