"Thanks for being my last stroke of luck!” In September 2015, Kwon Min, one of the top 0.1% students, accidentally uncovers the true identity of Cha Yubin, a mysterious student from the next class who appeared in his vision during a mock exam. For thirty minutes each day, the two unravel a mystery of fate and fortune more challenging than any test question, discovering fleeting yet radiant moments they wish they could hold onto forever, even as their D-Day draws near.