The story begins in Anpanman World, where everybody is bustling around, getting ready for the annual Star Festival. On that day, an egg emerges from Baikinman's garbage box, and when it hatches, a mysterious boy named Kurun emerges from within. Though Kurun does not know where he came from, he spends his days having fun with everybody. But one day, black stars begin raining down. Anpanman thinks that something suspicious might be occurring at the Star of Life, and he heads there.

Yakisobaman and Uncle Negi try to escort the young Pepper Trio and their important cargo to Vegetable Village in time for the carnival this evening but Baikinman and his gang are trying to steal the cargo. Luckily, Naganegiman keeps showing up to help fight them off, but how? Who could this mysterious masked swordsman be?

There is a world in which an endless rain of dark ash fills the sky, and covers the earth. Humanity, fearing the ash that burns and melts away human flesh, had no choice but to cover themselves in protective suits, and their faces with gigantic masks. Bundled up in their suits and hidden away behind their masks, the people have fled deep within the underground. This is the story of the children growing up in this fearful world.