The Yotsuba family's New Year's Reception brings together Miyuki and the other candidates to settle who will next lead their powerful clan. Winning the succession would mean Miyuki never again has to watch her brother Tatsuya live as an outcast. Yet the role almost certainly comes with a political marriage, and the prospect throws her into turmoil. Then the current head of the family makes a startling claim: Miyuki is not Tatsuya's sister. As the new year arrives, their relationship may never be the same. The film adapts the light novel's Yotsuba Succession Arc, blending action, romance and supernatural science fiction.