The story centers around Hida Kizuna, who visits the strategic defense academy Ataraxia at his big sister's request. "There, he encounters Chidorigafuchi Aine, a girl piloting the magical armor Zerosu. Aine suddenly pulls off her clothes before Kizuna's eyes. "Don't look, you pervert—" "No, you're the one?!" However, a communique about a serious mission arrives from Kizuna's sister. The mission—to rub Aina's chest?! Actually, Kizuna has the power to level up a girl through indecent acts. With a battle against another world, the future depends on this power.