After being betrayed by his country, Jirou left his past as a hitman behind and returned to Japan. In his eyes, nothing mattered anymore… that is, until he met Nami, an active hitman seeking vengeance for her father's death. But she isn't just any hitman; Nami is a wallman! Jirou is then brought back to the underworld, agreeing to team up with Nami and help her seek revenge.