Nikusuke discovers a sexy secret when he learns of the Gymnastics Of Darkness. Intrigued by the hot erotic potential of his new knowledge, the board chairman's granddaughter Tomomi helps Nikusuke pick an unwilling lady to be their first student. Miku must learn the meaning of excruciating pleasure under Nikusuke's gymnastic training, or lose the friendship of Tomomi. When Wakana finds out about the secret practice she too falls victim. Tomomi then has her two students lure a third young lady to the gym. When Yuu Aizawa finally gets there, she witnesses the secret Gymnastics Of Darkness.