Why is his name Untouchable?

Because he is a man who has never been in people's eyes. He just does something by his own feeling and his value is believing himself. It causes of his strange name and character, so no one notice him beside that girl, Bae Suzy. She is a lonely woman who is away from other people. Day by day, she lives for waiting her dead. She has no hope, no dream and she lives like a tree. 

Between them, what will happen?