Junitsu Kondo, known as "M," operates as a legendary hitman with accomplices, establishing his initial antagonistic role through his background as a professional assassin. Kondo first attracts Conan Edogawa's attention with suspicious behavior at a bathhouse. Believing Conan witnessed evidence of their bomb plot, Kondo and his partners kidnap him. They exploit Conan's apparent amnesia (later revealed as feigned), tasking Kondo with taking the boy to a Yaiba festival while outfitting him with a backpack containing remotely detonated explosives for an assassination. A shift occurs when Kondo discovers Conan avoided ingesting a sleeping pill. Instead of confronting him, Kondo retrieves the pill and later administers it to his female accomplice, defying expectations. He subsequently urges Conan to escape, revealing internal conflict over involving a child. Kondo's development progresses as he forms an alliance with Conan against the true mastermind, Tatsu, whom Conan deduces faked his death to manipulate events. Kondo actively assists in thwarting Tatsu's scheme to crash an explosive-laden truck into a vehicle carrying the children of the Nihorika First Minister. He facilitates police intervention by strategically placing a tracker on Tatsu's wife and alerting authorities about the bombs. His character arc concludes with a transition from antagonist to reluctant ally, directly enabling the plot's resolution by helping police locate Tatsu and safely dispose of the explosives.