"Mad Detective" made in Hong Kong is this year's surprise entry at the Venice Film Festival.
The movie stars Lam Ka-tung and Lau Ching-wan in a psychological thriller about a rookie police officer teaming up with a former colleague to bring a serial killer to justice.
Its multifaceted characters show "the many devils that animate our soul," Wai told reporters at a news conference on Thursday.
Wai also said the movie aims to show that "it isn't true that Chinese directors only make action-movies."
"Mad Detective" is the second consecutive Chinese movie chosen as the festival's surprise entry. Last year's mystery film "Still Life," by director Jia Zhangke, ended up winning the Golden Lion.
Both filmmakers said they were committed to making films in Hong Kong. "We are happy to make movies in Hong Kong" said To, when asked about how he would react if he were offered to work for a U.S. production house.
"We are trying to let Chinese directors grow," Wai said.
Festival director Marco Mueller introduced the surprise entry when he took creative control in 2004, adding a bit of intrigue and spice to the festival program. They have so far all been Asian films.