A package arrives and suddenly you're not an office worker anymore; you're twelve again in a fishing village, holding a marble that opens a door to somewhere impossible. The real magic isn't the flying girl or the lighthouse world, it's that you know, the entire time, this summer ends and your friend leaves and you can never go back. What destroys you is watching Nam-woo understand that too, watching him cling to Mari the way you cling to people you've already lost.

Nam-woo, now an office worker, gets a package from Jun-ho, a friend from his childhood, and it carries him back in memory to the last summer they spent together. They are in their hometown, a small fishing village, during the final days before Jun-ho goes away to a boarding school in Seoul. That summer, a marble and a deserted lighthouse could take Nam-woo to a fantastical world, home to a mysterious girl named Mari who can fly. The movie blends drama, fantasy and mystery.