welve-year-old Anna believes she sits outside the invisible magic circle to which most people belong, and shuts herself off from everyone around her.
Concerned for her happiness, Anna’s foster mother decides to send her to rural Hokkaido to stay in a sleepy town by the sea. As she dreams her days away amongst the marshes, Anna finds herself strangely drawn to the enigmatic house which sits upon the edge there. This is where she meets Marnie, an energetic young girl who seems to appear from nowhere. The pair quickly becomes inseparable. Although, whilst Marnie is cheerful on the outside, Anna begins to realise that she too harbours a deep sadness.
One evening, Marnie makes a heartfelt request of Anna: “Promise me something – that we’ll remain a secret, forever.” Anna begins to wonder about her newfound friend and is compelled to investigate the truth about Marnie and the mystery behind her sadness. As she is drawn deeper into Marnie’s world, she begins to learn about family, friendship and kindness.