Unexpectable Killing (1999)

Paul is a 30-year-old computer teacher with a modest monthly income, yet he has to support a family. After a drunken stint, he declares he'll do anything to earn a fortune. This is overheard by Ben, a former assassin, who decides to train Paul to become his successor. Over a year ago, Ben's lover suddenly disappeared, leaving him devastated and determined to train an even better apprentice to complete his career as a killer. After six months of training, Paul receives his first assignment, only to be surprised by his target. Meanwhile, Ben's missing girlfriend returns to Hong Kong...