In the first installment of a two-part film series, the storyline recaps the events of the television show. Mirai Kuriyama, the last descendant of a clan of warriors from the Spirit World, possesses the unique ability to wield her blood as a weapon against 'youmu'—beings believed to embody negative human emotions. One fateful day, while lost in contemplation on the school rooftop, Mirai encounters Akihito Kanbara, an uncommon half-youmu in human guise. In a moment of panic, she strikes him with her blood saber, only to discover his immortality. Thus begins an unlikely friendship where Mirai persistently tries to slay Akihito to bolster her wavering confidence as a Spirit World warrior. Eventually, Akihito persuades her to join the Literary Club, where they meet two other formidable Spirit World fighters, Hiroomi and Mitsuki Nase. As their camaraderie deepens, so does the threat posed by the youmu surrounding them. Their escapades will soon escalate into a battle for survival as they brace for the emergence of the formidable youmu known as Beyond the Boundary.