Hypn*tic Classroom

Girls normally show you a straight face, but they harbor secrets underneath.
The gap between them is erotically revealed!

Story
"With the art of hypnotism, you can bent your friends and acquaintances to your will!"
This is the slogan for a suspicious looking ring in a mail order catalog. The protagonist takes note and decides to buy it.
He reads the instruction booklet during class. It says:
"However, the effect lasts only for one day, and only once."
As he ponders on what to do, his eye falls on his English teacher.
He decides to go for it, and tells her she's suddenly extremely sleepy.
She promptly falls asleep.
As the classroom becomes restless, the protagonist awakens to a new sexual desire.
...With this thing, he could do a lot of things he never dreamed of...
What will happen next?