At the start of the new semester, everyone was Kokoro about class changes... but in fact, something unexpected happened! For some reason, there was only one girl in the boys' class! And she had huge breasts... For the boys in the midst of puberty, her H-cup breasts were too stimid! The boys couldn't contain their overflowing sexual desires, so Makoto, who has a timid personality, was used as a sex pet and done with as much as they wanted...