Inoue's motivation arises from the belief that Ishihara—later revealed as Shirahato's father—was falsely accused by the FBI for the Boston kidnappings and murder, resulting in his family's suffering and ostracization. However, it is later uncovered that Ishihara was guilty, and Inoue's family had actually entered witness protection, rendering the revenge plot futile. Their coordinated efforts culminate in an attempt to destroy the Hyper Linear train during its maiden voyage as a final act of retribution against the FBI and associated figures. Inoue's technical expertise facilitates sabotage of critical infrastructure, including redirecting MRI quench gases to incapacitate victims, demonstrating his integral role in the attacks. The character's background is confined to his involvement in the events of "The Scarlet Bullet," with no additional appearances or development in other Detective Conan media indicated by the available information.