A childhood apartment building becomes a ghost ship, and the show treats it like a character dying in real time. The animation doesn't just look gorgeous, it's doing the emotional work, making every flooded hallway and empty stairwell feel like a memory you're losing while you watch. Summer break becomes the space where kids learn that some things can't be saved, only honored on the way out.
Two sixth-graders explore their condemned apartment complex one last time before demolition, chasing memories through familiar hallways. When reality warps around them, the building detaches from the world entirely, adrift on an endless ocean with no land in sight. What was meant as a nostalgic goodbye becomes a desperate fight for survival as the structure creaks and groans around them, slowly sinking. Kousuke and Natsume must navigate both the physical dangers of their sinking home and something far more unsettling: the realization that this place holds deeper secrets. The building isn't just collapsing by accident. As they search for answers among the abandoned units and weathered corridors, they uncover connections to the other children trapped with them and discover that some bonds run deeper than friendship. The summer atmosphere of freedom and adventure twists into something haunting. This is a story about growing up, about saying goodbye to the spaces that shaped you, and about accepting that some people leave our lives whether we're ready or not. Atmospheric and melancholic, it captures that specific ache of childhood's end.