Makino Yayoi is a 16-year-old high-school girl. She made a promise with her mother that she wouldn’t have sex until she turned 20 years old! However she believes that promise to be in danger! She mistakenly thinks that her classmate, Suzuki, is “gunning for her chastity!” Now she must use every supreme technique she can as she defends her virginity with her life or she might grow a penis?!