Yoo So-joon is the successful CEO of a real estate company who has the ability to time travel when he takes the subway. Going back and forth in time, he sees his future self living a life of torment and unhappiness. To try to offset his doomed future, he decides to marry Song Ma-rin, a cheery photographer, even though he does not love her. Can Ma-rin help So-joon change his unhappy future?