Ban zhi yan

Roy comes back to Hong Kong after spending 30 years in Brazil. Despite having Alzheimer's, he holds a half smoked cigarette in his pack because it was a memento from the girl he loved. Upon arrival, he meets a rascal named Smokey, who is trying to find out who his father is and is always videotaping a policewoman, with who he has an infatuation for. The two form a lasting friendship as they try to help each other out in their quests (imdb)