Yura Yamato is a shy girl who enrolls in Stella Women's Academy. On her first day at the academy, she checks into her dorm to find that her roommate, third year Sonora Kashima is out visiting her family. Looking around the room, she discovers her roommate's collection of military items, such as guns, action guerilla movies etc. At the same time, the C3 Club meets elsewhere in school to discuss the recruitment of new students into the club. After coming up with a ridiculous plan and deciding that it would be unrealistic, they decided to take a break and play a Rambo-style battle to lighten the mood. Rento goes to Yura and Sonora's room to borrow Sonora's M60 and unexpectedly stumbles onto Yura playing with the "props" while watching Rambo. Deciding that yura fulfilled the condition to be recruited, she brought Yura to the C3 Club.

Sonora challenges Yura to a one-on-one match, matching each other move for move and rekindling their excitement for airsoft. In the middle of the match, Rento comes by to give Yura some more ammo, earning her thanks for inviting her, whilst Karilla comes to support Sonora, with the entire club soon getting involved and turning the game into a free-for-all. As the day comes to a end, Yura urges everyone to keep fighting til the last pellet is fired, bringing everyone into her dream world where they fight against the entire academy. With the day finally coming to an end, Sonora invites Yura and the others to come visit her any time. After Sonora leaves for America, Yura takes some initiative and invites some other students to join the C3 Club.