The series takes place at a school known as Seishou Academy. Unlike average school, all the students are actually anthropomorphized guns, training to one day become a useful weapon, and is divided up into elementary school (sub-machine guns, utilizing 9mm rounds), middle school (assault rifles, utilizing 5.56mm rounds), and high school (battle/sniper rifles, utilizing 7.62mm rounds). All students in Seishou trains to shoot their target (literally) using live ammunition. The series mainly focuses on an FN FNC assault rifle nicknamed Funco and her friends.
Funco, Ichiroku, Eru and Sig go on a camping trip in the mountains where they do some fishing in the river, smash a watermelon and relax in a hot spring. Later as the girls turn in for the night, Funco and Sig make a promise that they'll always be together.