If you loved I Am Sun Mu, try The Soul-Mate
A bridge between a film you've already seen and one most people haven't. Here's what they share, and what the second one does that the first one doesn't.
What The Soul-Mate is
It seems South Korea is contractually obligated to produce one of these a year. A ghost asks a human, who can see him, to solve the crime that led to his death. It ticks off every genre box imaginable, for better or worse.

