On his way to school, Hiiro Ryuugasaki stumbles upon a mysterious voice emanating from his storage shed. Upon investigating, he uncovers a smartphone with the popular card game 'Shadowverse' pre-installed. Assuming it's a gift from his grandfather, Hiiro remains unperturbed. However, when news surfaces about his classmate Mimori Amamiya falling victim to a notorious player named Takuma Kibakura, who snatches phones from defeated opponents, Hiiro decides to act. Determined to help Mimori, Hiiro dives into the thrilling realm of Shadowverse, where he faces off against skilled adversaries like the formidable Lucia Yonazuki in high-stakes battles.