Hibiki lives with her younger brother and father. Hibiki, who cares for her younger brother, warns her AV-loving father, "What will you do if your younger brother sees this?" But one day, her younger brother accidentally watches his father's AV. He mistakenly thinks that sex is something scary and comes crying to Hibiki. In order to correct his younger brother's sexual knowledge, Hibiki uses her own body to teach him about real sex...