Yuki grew up in a poor but peaceful family, cherished by her grandfather, father, and older brother. One day, while playing together, her brother teases her with a sexual prank. Still too young to understand its true meaning, Yuki is left only with shock and embarrassment. That night, her father returns home and asks Yuki to give him a massage. During the session, he becomes aroused by her body and forcibly penetrates her undeveloped pussy. In an instant, the family's warmth collapses, bringing a drastic change to Yuki's life.