One day an idol is bitten by a zombie and before she is taken into custody, she runs away. She only has 72 hours left until she becomes one, so she tries to find the zombie serum, but high school girl zombie hunter and zombies attack her. Will she make it to the destination within the time limit?

On Earth in the near future, humanity faced imminent destruction from mysterious giant creatures known as "Huge." The entire world unites against the Huge, and successfully develops weaponry known as "CHARM" (Counter Huge Arms) by combining science and magic. CHARM exhibits high rates of synchronization with teenaged girls, and the girls who use CHARM are viewed as heroes called "Lilies." Throughout the world, "Garden" military academies are established to train Lilies to face the Huge and to serve as bases to protect and guide people.

Riri Hitotsuyanagi managed to pass the exam to enter the prestigious Garden known as Yurigaoka Girls' School. She entered in an attempt to find Yuyu Shirai, a girl who rescued her in her past. This is a story about Riri and other girls who aim to become Lilies at one such Garden.