The world changes almost overnight when mysterious spheres appear in the sky, forcing high school students in Seongjin High School into military service. What used to be ordinary days quickly turns into a fight for survival, where fear and loss become part of everyday life. Among them is Jo Jangsoo, quiet and dependable, someone people rely on without realizing it. And then there is her—distant, composed, and unwilling to let anyone get too close. At first, they are nothing more than teammates. But in the middle of chaos and uncertainty, Jangsoo begins to stay in the moments where she feels most alone. He doesn’t ask for anything, doesn’t try to break her walls—he simply stays. Slowly, something begins to change. Without words or confessions, a quiet connection grows between them, built on presence, trust, and the need to hold on to something in a world that keeps falling apart. And in the end, after everything they’ve lost and everything they’ve survived, they find themselves still standing—side by side, choosing each other in a world that almost ended.