Kazusa is an adult (who looks just like a middle-schooler) that is coincidentally the new school doctor of the primarily female Wakabane Middle School! He knows everything about how the female body works, so just what lies in stock for our supposedly not-perverted hero?!
[Wikipedia](https://ja.wikipedia.org/wiki/%E3%81%BB%E3%81%91%E3%82%93%E3%81%AE%E3%81%9B%E3%82%93%E3%81%9B%E3%81%84)
