In a futuristic Neo-Tokyo, crime is rising rapidly in the wake of a new generation of super-drugs capable of enhancing the user's physical and mental abilities. Hajime Tsukomo is a new recruit on a federal task force trained to go after these powered-up criminals. Now he must team up with Zeroichi, a so-called Hanger looking to reduce his own jail sentence in exchange for helping to take down these chemically-boosted bad guys.

Afraid that Hajime could suffer the same tragic fate as his previous Keeper, Zeroichi intentionally widens the emotional distance between them for Hajime's own safety, leaving a frustrated and hurt Hajime doubting the kind of relationship they really have. Unfortunately, finding the time to sort out their feelings isn't a luxury either of them can afford— not with the mysterious group responsible for the death of Zeroichi's former Keeper suddenly terrorizing Neo-Tokyo once more.

In the face of even greater danger and higher than ever stakes, Zeroichi must learn to move past the fear that has been driving them apart and rely on Hajime as a true partner.