Don't Worry, I'm a Ghost(2012)

A man wakes up in the hospital after an accident with no memory of his name, family, or home. After the police identify him as Lee Mungi, he returns home, only to wake up and find a girl watching him. She claims to be a ghost. Mungi dismisses her as a hallucination until he finds her photo at a funeral and learns her name is Kim Yeonhwa. When he asks if she wants him to find her killer, Yeonhwa says the police can handle that and reveals that he has a more important task. The reason she came to him lies within his lost memories.