Sasamoto

Sasamoto is respectful toward Watanabe and enthusiastic about meeting Kogoro Mouri. His admiration for Kogoro gives his relatively small role a light comedic element amid the film's more serious investigation.

He remains cooperative during the police response and does not object to the involvement of the visiting detective. The film gives him less individual characterization than Watanabe, with the pair generally functioning together as the Niigata investigators assigned to the case.

Sasamoto is an ordinary human with professional police training. His duties involve standard investigative work and supporting the official response to the crimes around Kitanosawa.

No exceptional fighting style, deductive specialty or other distinctive ability is established for him. He functions primarily as a supporting investigator rather than one of the film's principal detectives.

Sasamoto appears during the police investigation in Kitanosawa, where Conan Edogawa, Kogoro Mouri and their companions have encountered a group of former residents connected by events from eight years earlier.

He works under Watanabe as local police examine the circumstances surrounding the death of Shogo Hikawa. Their investigation runs alongside Conan's increasingly independent search for connections between the victim, the old village and earlier crimes.

The case ultimately expands into a conspiracy involving Keisuke Yamao, the submerged old Kitanosawa and an attempt to destroy the dam. Sasamoto remains part of the official law-enforcement response while Conan pursues the culprit.

Watanabe is Sasamoto's senior colleague in the Niigata Prefectural Police. Sasamoto assists Watanabe during the investigation at Kitanosawa.

Kogoro Mouri is a famous private detective whom Sasamoto admires as "Sleeping Kogoro."

Conan Edogawa participates unofficially in the same investigation and ultimately uncovers the deeper connections behind the incidents.

Shogo Hikawa is the victim whose death brings Sasamoto and the local police into the central Kitanosawa investigation.