Shizuto Kumiyama, elder brother to detective group member Shigeno Kumiyama, initially alerted his sister to Tokito Mikagura's disappearance. He sent a letter stating he had seen Tokito at a church in a foreign location, prompting Shigeno and her companions to travel abroad in their search. His own independent investigation into Tokito's whereabouts hit a significant obstacle described as a "wall of silence," preventing him from uncovering more. He expressed deep concern for his sister and the other detectives, fearing they might encounter danger. Despite these risks, he committed to supporting their efforts to the best of his ability. Shizuto operates legitimate businesses, a stance that brought him into conflict with local criminal organizations. These groups sought to eliminate him due to his interference with their illicit activities, creating additional challenges that dogged his environment. Two years after Tokito's disappearance, Shizuto sent another letter to Shigeno. This communication contained rumors of Tokito being sighted in the city of Dalian, serving again as a catalyst for the detective group to pursue new leads across the sea.