Hana and Tetsuya, who lived in the same neighborhood for a long time and were childhood friends, became siblings when their parents got married. Hana, who suddenly becomes a family, builds a wall with Tetsuya and feels lonely. . Out of curiosity, she offered to pretend to be a doctor again and let Tetsuya touch her massive breasts... From that day on, I was caught up in my younger brother's blue sexual desire that I cannot be controlled.