Pained (2011)

After losing his family when he was young, Nam-soon feels no pain. He cannot feel physical pain and is emotionally barren until he meets Dong-hyeon, who calls herself a vampire because she suffers from hemophilia. Unlike Dong-hyeon, when Nam-soon is injured, she bleeds from even the smallest wound. As the two grow closer, Dong-hyeon suddenly begins to lose his lifelong insensitivity to pain and the hurt of a lifetime washes over him.