One day, Yuka (31-year-old married woman), a teacher who runs a cram school at home, decides to give one-on-one lessons to her poor student Hiroyuki to improve his grades... However, Hiroyuki, who is in his teenage years, is distracted by things other than his studies and has a hard time concentrating. Yuka, who is trying her best to teach him, does not notice that her bra is floating up on her chest and her nipples are visible, and when the student Hiroyuki sees this, he becomes even more unable to concentrate on his studies...