Sumikkogurashi debuted in 2012 as slightly negative characters who like to stay in the corner of a room. The characters include "Shirokuma", a polar bear who is sensitive to cold, "Penguin?" (with a question mark in its name), a penguin who is unsure if it is actually a penguin, "Tonkatsu", a piece of pork cutlet that was left uneaten, "Neko", a shy cat, and "Tokage", who hides his nature as one of the last dinosaurs. The franchise has inspired toys, books, stationery material, video games—and now a feature film.

Set in the town where the Sumikkogurashi characters live, the film follows a mysterious tale that takes place on the night of the great blue full moon that occurs once every five years.

At an old factory on the edge of the forest, the Bear Factory Manager invites the Sumikkos to make toys. They make use of what they are good at, and complete their stuffed toys. The Sumikkos are motivated by the praise of the Bear Factory Manager. They have matching uniforms, delicious food, rooms to stay for the job, .and spend their days making one toy after another. Then, the toys that were shipped to Sumikko's town start moving around. There is something "mysterious" about this factory.