Born during a time of despair and trained as a killer, Zense is the oldest and deadliest biological weapon that the government has.
Sent on a final mission at the age of twenty-four, Zense has one last target to kill before he can retire. The modified human soldier studies the file of his latest target - a powerful Overlord of the Underworld known by only his pseudonym Ouroboros.
As Zense closes in on his target, he discovers that Ouroboros was a person different from his mission file. The Mafia Lord was kind to his people and fought on the wrong side of justice. Conflicted, Zense hesitates to kill Ouroboros.
Unable to withstand the pressure of Ouroboros' growing power, the world government sends in other assassins to get rid of Ouroboros and Zense.
As the genetic modifications done to his body began to fail, Zense has to make a decision. Kill Ouroboros and spend his remaining time in peace or take Ouroboros' side to fight against the world till his last breath.