Netflix announced a spinoff of its 2023 Korean thriller Kill Boksoon. With the working title Mantis, it will feature Yim Si-wan, Park Gyu-young, and Jo Woo-jin in the lead roles.

Set in Kill Boksoon's own world of contract killers, Mantis follows assassins Mantis, Jae-yi, and Dok-go. The SEE AT Film Co production will star Yim as Han-ul, a contract killer, also called Mantis, who works for an organisation called MK Ent. In Kill Boksoon, Cha Min-kyu makes a brief mention of Mantis as a character who has "gone on a vacation". The spinoff film will revolve around his comeback to the world of crime, searching for new opportunities. When Mantis comes back, he comes across Jae-yi (Park), a fellow trainee and his old friend, and legendary assassin and MK Ent founder Dok-go (Jo).

Lee Tae-sung, who worked as assistant director on Kill Boksoon, makes his directorial debut with Mantis. Kill Boksoon director Byun Sung-hyun and Lee have written the screenplay.