Zero is an assassin employed by The Adjudicator, and the leader and mentor of his own group of assassins. He is the secondary antagonist and a major opponent in John Wick: Chapter 3 – Parabellum, during which he fights against protagonist John Wick on several occasions.
Zero is a trainer of a group of ninja-assassins. When not teaching, he works as a street-food sushi-chef. He is a fan of John Wick.
Events of John Wick: Chapter 3
He and his students are hired by The Adjudicator to take out anyone she deems disloyal to The High Table or guilty of aiding John Wick following his excommunication. John and Zero meet up at the Continental following the deconsecration and engage in a duel where Zero is fatally stabbed.
Despite his job as an enforcer, Zero does not seem to let it affect his personal life. He seems to take extraordinary enjoyment from fighting, and both he and some of his students are big fans of John Wick to the point that they let him recover between fights instead of hitting him when he's open; during their fight in The Continental, he quickly admitted to Wick that he's a huge fan of the latter's work and abilities.