In the context of tense international situations, Tokyo has become the focus of all forces. A certain major country announced that it would donate the Loyal Soul Memorial Tower to Japan, which aroused the suspicion of some knowledgeable people. Young detective Homura Roku accidentally learns of rumors about the "secret job" of Yoshiji, a mason at Tsukiji Public Baths, and takes the pseudonym Masaki Shota to get involved. He discovered that special plaster was used at the construction site, and he judged it to be related to a certain great country by its smell. However, the enemy noticed something strange and the clue was interrupted. But Homura did not give up. He remembered the irregular piling sounds near the construction site and re-launched the investigation with the help of a self-recording seismometer. At this time, the foreman Gorozo discovered the giant cannon hidden at the construction site. What threats will he face? Can Homura stop the enemy's conspiracy in time?
