Fulltime Killer( simplified Chinese :全职杀手; traditional Chinese :全職殺手; Cantonese Yale : Chuen Jik Sat Sau; pinyin :Quanzhi Shashou; literally "Fulltime Assassin") is a 2001 Hong Kong action drama film co-produced and directed by Johnnie To and Wai Ka-Fai , and based on Pang Ho-Cheung 's novel of the same name. It is informally known by its Hong Kong English working titleYou & I.

Based on a book by Hong Kong filmmaker Edmond Pang Ho-Cheung ,Fulltime Killerprotagonist O is a hitman being challenged by new hotshot Tok. O has lived a life of seclusion as the number one hitman in Asia . The woman living at his contact address is captured after O foils a set-up by his boss. He then goes on the run whilst trying to fend off his adversary. The last part of the movie focuses on an Interpol detective's attempt to write the story of Tok and O.