Haruma Kawagoe is an only child. Long ago, during Christmas, his mother miscarried the baby who was to be his sister. That night, young Haruma knelt and prayed earnestly: "Please make my mother well again, and please give me a little sister." Years have passed, and Haruma has nearly forgotten his prayer. But Santa hasn't... One Christmas, when Haruma least expects it, he receives an unusual gift: his sister.