Their ship sinks on the voyage home, and after two nights adrift, five people wash up on a deserted island. With no water, no shelter, and no promise of tomorrow, Seo Do-yun is determined to bring everyone back safely. Haerin, who hides her sense of responsibility behind cold judgment; Jisu, who puts herself last while caring for others; Narae, who masks her anxiety with laughter; and Somin, long accustomed to being called his old friend. As they share sips of water and scraps of shade, the distance between him and the four slowly begins to change. The more nights they endure together, the more kindness stops meaning the same thing. Someone reaches out first, while someone else stops at the line called "friendship." The will to make it home alive, and the wish not to lose these feelings. Can confessions that began on a deserted island continue beyond its shores?