A boy drowning in grief meets a girl who shouldn't be able to feel anything, and the show spends thirteen episodes proving him wrong. The animation doesn't just look beautiful, it moves with the specificity of someone who knows exactly how a person breaks and rebuilds themselves. By the end, you're not watching a romance unfold; you're watching two people convince each other that the future is worth wanting again.

Natsuki returns to his flooded hometown carrying the weight of lost years and a lost limb. His grandmother's debts loom over him, and her sunken laboratory holds the only promise of a way forward. When a suspicious debt collector named Catherine offers him a chance, he sets out with her to search the ruins beneath the waves for a treasure his grandmother supposedly left behind. What they find is not treasure but a girl named Atri, a robot so humanlike in looks and emotion that she could pass for a living person. Grateful to be rescued, she tells Natsuki that his grandmother gave her an important mission, though she can no longer remember what it was, and vows to serve as his leg until she fulfills it. Natsuki first means to sell her, but the chance to reconnect with his grandmother's research through Atri makes him think again. The story blends science fiction, drama and romance as a boy and a robot girl spend a summer together in a small town slowly sinking into the sea.