Shinji Mizushima leads an ordinary student life with no particular distinction in academics or athletics. One rainy afternoon, he sees the school's mysterious new transfer student Amane Satonaka standing alone outside in the downpour without an umbrella, humming a quiet and melancholic melody to herself. The sight stops him completely. Something about her presence seems to exist on a different register than the world around her. He is still watching when he realizes she is about to collapse. He runs to her and catches her. He does not yet understand what that moment has set in motion.