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's ordinary adult life shatters when an unexpected package arrives from Jun-ho, his childhood best friend. Inside is a marble, and holding it pulls him backward through time to one specific summer: the final days before Jun-ho boarded a train to Seoul, leaving their small fishing village behind forever. That summer wasn't ordinary. A crumbling lighthouse at the village's edge became their secret gateway to somewhere else entirely. A world where gravity bends wrong, where the sky refuses to stay put, and where a girl named Mari exists in defiance of every rule reality should enforce. She moves through the air without explanation, speaks in riddles, and seems to know things about Nam-woo he's never told anyone. Now, as an adult returning to these memories, Nam-woo must piece together what really happened that summer. Was Mari real or shared delusion? What did Jun-ho see that Nam-woo didn't? The marble holds answers, but uncovering them means reliving the exact moments he's spent years trying to forget.