Shinju Caine is a master of every known God Slayer magic, a protective older brother to his two younger siblings, Nagato, who uses all known Dragon Slayer magic, and Marco, who uses all known Devil Slayer magic, best friends with Shido Itsuka, and wishes to marry his homeroom teacher, Tamae Okamine. During a spacial quake, he and Tamae get locked out of the shelter designated for the school, and he confesses to Tamae, who eagerly accepts. Now, their lives are about to take an interesting turn.