Haru is a high school student who prefers his privacy over spending time with his sister, Yui. But his monotonous life changes when a simple game with her comes to life, and a mysterious light swallows the two siblings.

He then finds himself in an unknown world, far from her. A place where magic is real, and to find her, he must now learn to adapt, develop a new talent, and with the help of new allies, uncover the world's mysteries to fulfill his promise to protect her.