The action " KILLER is DEAD” takes place in the near future. The world is very similar to the one in which we live but still different. The player controls an executioner named Mondo Zappa. His right hand wields a katana, and the left hand is wholly modified (it can be changed into various forms, including a gun and drill). His goal is to execute heinous criminals scattered all over the world.

Playing for Zappa, you will go through twelve story missions selected on the world map. They range from short linear levels to longer levels that require complete investigation. Some level areas also need the activation of interactive objects (e.g. switches) to move forward. During missions Mondo fights with challenging enemies, using a katana and cybernetic weapons. If you use your left hand, camera's angle changes view to the perspective over the shoulder.

There are three types of missions in the game: story missions (advance the narrative forward), submissions (they are set at the main missions where Mondo performs various tasks ranging from combat missions to quests), and" Scarlet " missions where the female Starlet support character issues combat missions.