O is considered the greatest hitman in Asia. Outside of the job, he lives a reclusive existence in an apartment in Hong Kong.
Lok is an eccentric, flamboyant assassin who wants to discover O's identity and claim the top title for himself.
Chin answers an ad on a bulletin board and accepts a job as the cleaner for O's flat. Lok soon insinuates himself into her life in what's half a courtship, half an attempt to figure out who O is and how best to kill him. It turns into a bizarre love triangle between Chin, O, and Lok, with none of the three quite sure of the others' motivations.
Finally, there's Albert Lee, an Interpol detective who's out to arrest them both, and who ends up writing a book about the case.
''Fulltime Killer'' is a 2001 Hong Kong action film starring Andy Lau, Takashi Sorimachi, Kelly Lin, and Simon Yam. It's a strange action-comedy that plays around with flashbacks and points of view, and almost requires multiple viewings to truly understand.
* AnachronicOrder: The early part of the film has a bad habit of not labeling its flashbacks very well at all.
* ChekhovsGun: [[spoiler: Lok's epilepsy.]]
* FriendlyEnemy: Despite the fact that he's out to kill him, Lok actually likes O a great deal and they're downright chummy by the end of the film.
* HitmanWithAHeart: O's style is slow and deliberate, and between hits, he's reclusive and downright shy.
* ShoutOut: The final showdown between O and Lok takes place in an isolated warehouse full of hidden weapons that Lok compares to ''MetalSlug''. Both of them turn out to be huge fans of the game and run into the encounter with big smiles on their faces.
* ThereIsNoKillLikeOverkill: Lok ambushes an Interpol strike team near the end of the movie with a Barrett M82 ''anti-materiel rifle''. A graze wound from it is enough to put Lee's partner into intensive care, and it's heavily implied she did not survive.
* TwistEnding: The last third of the film takes a weird turn for the bathetic, as we follow an alcoholic Lee as he tries to write a book about the case. [[spoiler: Chin's version of the final showdown between O and Lok involves a shootout in a warehouse that stored fireworks, and O is shot dead after being flash-blinded by an accidental explosion. After she leaves, Lee realizes that in her version, Lok would've been driven into a grand mal seizure by the fireworks display and would've been helpless, which means the entire thing is something Chin made up to make Lee think that O is dead and Lok is alive.]]
* UnreliableNarrator: [[spoiler: The movie following O and Chin's escape from Interpol is a version of events told to Lee by Chin, as Lee attempts to write a memoir on the case. It's only after she's left that Lee realizes that it's probably not an ''accurate'' retelling.]]