Oh, the Mysterious (2017) Korean Drama

Il Seung was wrongly accused of a crime and imprisoned, and has spent ten years on death row. He manages to break out of prison and somehow becomes a fake cop, then sets out to find a hidden stash of 100 billion won (nearly 100 million dollars) on behalf of criminals who will supply him with a new identity upon receipt. He has three days to find the cash and begin his new life.