Novelist Kagamizuki Masamune was suspected of a murder case while traveling... The third installment of the full-scale mystery adventure series. The mystery adventure "Izumi Jiken File" series is a mystery adventure game that "deduces the culprit" based on the situation at the crime scene and the information collected by interviewing. The best-selling author "Kagamizuki Masamune" who always goes on a sudden trip, and the new editor "Izumi Kido" who is in charge of it. Three days before the deadline for the new manuscript, Izumi, who is heading to Kagamizuki's apartment, receives an email. "It's become a big deal. I want you to help me. Please come to Kirishimayama Ryokan in Kagoshima as soon as possible." A hot spring inn wrapped in the fresh greenery of Mt. Kirishima. There was a figure of Kagamizuki who was suspected of murder... In the open-air bath where there was a murder case, there are employees at the entrance and "Yoshizu" around it, so it is impossible to commit the crime from the outside. It seems that the five men who used the open-air bath were forced to wait at the inn as suspects of the incident. At this rate, my name as a novelist will be scratched. In order to clear Kagamizuki's suspicion, Izumi challenges to solve the case.