This gentle chapter book by Yoriko Tsutsui explores the universal experience of sibling responsibility and the anxiety that can accompany it. Anna, the older sister, is left in charge of Katy, who then wanders off. The narrative follows Anna's journey of fear, determination, and eventual triumph as she searches for and finds her sister. The book handles the sensitive topic of a lost child with a mild, reassuring tone, focusing on Anna's proactive problem-solving rather than prolonged distress. The emotional arc moves from initial worry to a heartwarming resolution, emphasizing Anna's growth in confidence. This book is ideal for children aged 4-8 who are learning about responsibility, have younger siblings, or are navigating feelings of worry. Parents might reach for this when discussing the importance of staying together, or to normalize a child's feelings of anxiety when caring for a younger sibling. The illustrations are important for conveying emotion and setting. It stands out by centering the older sibling's emotional experience and agency in a common childhood scenario.