Hiroshi is a pervert. when he accidentally saw Tetsuko, he fell in love with her, and jumped to her chest. Of course, he got turned down. Angry, he kicked a trash bin, that flew right to head of passing near girl Sora. Luckily, that saved her from a falling down сonstruction beam. Sora is an army maniac from a wealthy family, and she decided to return favor of saving her life to Hiroshi, so she accepted the "mission" that he proposed to her: get him girlfriend, or "woman that let him touch her ass and breasts". After the first step - transporting Hiroshi's all-boys school classroom to the rich all-girls school by helicopters, their hilarious school life starts...

DEFCON = DEFence readiness CONdition, see Wikipedia for more info.