In the near future, a skilled fighter is part of an elite squad of commandos known as the 701 Squad, which has undergone a special procedure to feel no pain. After the government disbands the squad, he decides to escape the life of violence and hides under a new identity as a quiet librarian. However, the peace is short-lived when his former squad members begin a ruthless crime spree, using their unique abilities to rob banks and commit murders across the city. Feeling responsible for their actions and disturbed by the violence, he dons a black mask to conceal his identity and decides to stop them, breaking his vow of leading a peaceful life.

His efforts to combat the crimes of his former teammates draw the attention of the local police, particularly a determined and insightful detective, who begins to see a pattern in the attacks and suspects the involvement of an insider with advanced combat skills. Meanwhile, the former commando finds an unlikely ally in a feisty research scientist who is the key to unlocking the secret behind the squad's superhuman abilities. Together, they embark on a dangerous mission to stop the squad's diabolical plan, which threatens to plunge the city into chaos. As he battles against his past and the formidable foes he once called brothers, his quest for redemption becomes a violent struggle for survival and justice.