Manami is a 25-year-old new teacher. Her sexy figure and revealing clothes often give people the wrong impression, but she is a kind teacher who cares about her students. However, she has a hard time dealing with three naughty boys. Naoto, Ryuta, and Takeji are in the third grade and are at the age where they are just starting to become sexually aware, as they play pranks on Manami's plump body. They do whatever they want, from groping her breasts and lifting her skirt when they greet her, to peering at her panties during class and making breasts out of clay. However, the boys are not satisfied. This is because the 'vital parts' are hidden in the porn magazine. As the naughty boys escalate, they finally find out what is important during gym class...