Seisaku Nakamura was born around 1924 in Shizuoka Prefecture, Japan. Despite being deaf, he was intelligent and achieved high academic marks. However, he faced ostracism from both his family and society due to his disability, leading to social misfit behaviors. Nakamura developed an obsession with samurai culture and enjoyed films depicting assassinations using Japanese swords.

According to his testimony, Nakamura's criminal activities began on August 22, 1938, at the age of 14, when he attempted to rape two women who resisted, leading him to murder them. These two murders are often excluded from his confirmed killings. On August 18, 1941, he killed a third woman and injured a fourth. Two days later, on August 20, 1941, he murdered three more individuals. On September 27, 1941, Nakamura killed his brother and injured his father, sister, sister-in-law, and niece. His final known crimes occurred on August 30, 1942, when he murdered a couple and their two children and attempted to rape another daughter.

During wartime Japan, information about his crimes was restricted to avoid public panic. His family was aware of his actions but feared retaliation and societal shame, preventing them from coming forward. Nakamura was arrested on October 12, 1942, and confessed to nine murders, with some sources suggesting he admitted to two additional killings. Despite medical professionals deeming him insane, he was swiftly tried under wartime laws and executed by hanging on June 19, 1943.