Every year for the past 67 years, the people of the isolated island of Lumière have suffered an event called the "Gommage", where an entity, known as "the Paintress", paints an ever-decreasing number, and all humans with an age above that number disappear. Every year after the Gommage, Lumière sends an Expedition of volunteers to head to the mainland in an effort to slay the Paintress before she can paint a new number.