The Seat-Stealer: Save Me Now, or I’ll Run for Office

[Underworld + undercover cop + calculating protagonist + ruthless + no bleeding-heart heroics + multiple heroines]

When a gang boss dies suddenly, an undercover cop who looks just like him takes over his identity. He moves into the boss's mansion, spends the boss's money, looks after the boss's wife, and leads a host of underlings as they keep expanding their turf. As he walks a razor's edge on his undercover mission, he continues climbing to ever greater heights... Until, in the end, he becomes the pride of Hong Kong... and gets nominated...