As Yura Yamato enters the high school section of Stella Women's Academy, she receives an invitation from Sonora Kashima to join the C³ club - a group dedicated to military survival games - of which Sonora is now the leader. Alongside Sonora, two second-year students, Karila Hatsuse of Japanese descent and Honoka Mutsu who wields a G36K, are also members, as well as two newly arrived students - Rento Kirishima from a family of Japanese sweets makers, and the petite Yachiyo Hinata.