The story follows the travels of Hazuki Azuma, a tall, brooding high-school girl, as she searches for her adopted older sister, Hatsumi. On Hatsumi's 16th birthday, she suddenly disappears right in front of Hazuki! Hazuki manages to follow Hatsumi with the help of a yellow parakeet named Ken, and ends up in a place called "The Great Library," full of different exotic worlds. But Hatsumi is not to be found easily, and so the search begins. Lilith is a caretaker of this Great Library, a repository containing all of the worlds in the universe stored within books. Each episode of "Yamibo" details another one of her lives among the many worlds and follows the adventures of Hazuki, Gargantua, and others in search of the girl Hatsumi, whom they've known by different names.