Tending to his sister, who is paralyzed after a fall from a tree, Tatsuya Kitazaki wants revenge. Yet, just as he is about to cut down the tree, a strange and seemingly ageless girl, Sara Nishikujo, appears to stop him. What's more, the girl seems to have the ability to communicate with plants—and she tells Tatsuya the tree's version of his sister's accident. This marks a watershed in Tatsuya's life, as everything begins to change.