After a successful first season, Webtoon "Assassin Jun" is about to begin it’s second season. Out of ideas, Jun uses an anonymous email's plot in his Webtoon, only to see real-life terrorist attacks resembling the story unfold.

Hitman: Agent Jun tells the story of a former legendary secret agent who decides to retire and become a comic book writer. However, his peaceful life is disrupted when his true identity is revealed and he is forced to return to his old job as a national intelligence agent. With the help of his colleagues, he embarks on a mission to expose the corrupt officials who framed him, all while balancing his newfound career as a writer.