Jae-joon used to be a promising young CEO of an IT company, until he unexpectedly becomes a postman. He delivers the letters grieving people have written to their loved ones in Heaven. One day, he comes across Hana, who writes a letter full of resentment to the dead man that she used to love, and reveals his presence to her. Jae-joon proposes that Hana delivers responses which come back from Heaven and the two think up various ways to give peace and happiness to those who are alive and left behind, sometimes by writing the responses themselves. But a human being and a postman from Heaven cannot spend unlimited time together. As they start to grow feelings for each other, Jae-joon tries to pull himself away from Hana and the two, for the last time, deliver a response to an owner of a coffeehouse who had been agonizing for a long time over the loss of his son.